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7th Grade Heredity
Transcript of 7th Grade Heredity
- Friar in the 1800s
- because of his experiments with the pea plants he is considered the father of genetics. When Mendel bred plants with purple flowers together they produced only purple flowers. When Mendel bred plants with white flowers together, they produced only white flowers. + When Mendel bred plants with white flowers together with purple flowers what do you think happened? Let's watch a video and see if you change your mind First, lets get the definition of a hybrid.
A hybrid is the offspring of two animals or plants with different forms of the same trait. Terminology So for example, if a person with 2 brown eyed traits were to have a baby with an individual with two blue eye traits, this baby could be considered a hybrid for this trait. Hybrid + = hybrid Mendel also discovered that when organisms reproduce, each parent contributes traits for the offspring. Dominant and Recessive Traits Today this seems obvious to us as kids can look a lot like their parents with traits from either side. Each trait that you have either visible or not can be traced back to your genes. A dominant trait can allow a certain trait to be expressed such as curly hair. NO, Not those kind of jeans! Genes! Your genetic code! Dominant trait: a genetic factor that blocks another genetic factor. However, if a dominant trait is not present from the genetic make up of an individual then a recessive trait can be expressed. recessive trait: a genetic factor that is blocked by the presence of a dominant factor. Chapter 19: Genetics
page 645 – 653 IScience What controls traits? Chromosomes are string like structures that exist in the nucleus of a cell.
In humans we have 23 pairs. Each pair consists of two chromosomes one from each parent. These chromosomes hold genes. A gene is a section on a chromosome that has genetic information for one trait. Each gene can have different forms called alleles. Alleles are different forms of a gene. In Mendel's pea experiments the hybrid pea plants had two alleles for flower color. One for purple and the other for white. Take:
- a third of a piece of paper
- a pair of scissors
- a marker or colored pencil It's time to create a graphic organizer. Step 1: Fold the paper into thirds.
Step 2: On the outside flap write: chromosomes hold genetic information and draw a picture of a chromosome.
Step 3: On the inside flap write: genes hold specific genetic information for specific traits and draw a picture of a gene on a chromosome.
Step 4: In the middle of the paper write: each gene can have different forms called alleles.
When you have decorated your graphic organizer to help you remember this information, put glue on the back middle. Glue this into your notes in the space provided. In your notes we are going to build a graphic organizer to help up remember this information. Phenotype Genotype What's the Difference? A phenotype is how a trait appears or is expressed. A genotype is the genetic makeup of an individual (the alleles present).
So our brown eye person could have a genotype of Brown blue or Bb. One dominant brown allele and a recessive blue allele. We use letters to represent the genotypes for a specific trait.
Homozygous dominant: BB
Homozygous recessive: bb Chapter 19
pages 656-659 IScience Chapter 19
pages 660-663 To remember that info... Take one piece of paper and fold it almost in half so that it overlaps the far edge by one inch.
Take another piece and fold it almost in half, but make it overlap by two inches. Put the two papers together so that they fit inside one another and you get four flaps facing you.
Staple them at the fold. On the outside top flap write: INHERITANCE PATTERNS On the next flap write: Types of Dominance Then on the inside make three columns and place in the columns: dominant trait will be expressed dominant-recessive interactions ex. Mendel's Pea plants Incomplete dominance when the alleles of a gene mix together like paint. ex: straight ear allele of a dog mixes with floppy ear allele to make a medium floppy ear. co-dominance both alleles can be observed in a phenotype ex: a red haired cow and a white haired cow produce a cow with both red and white hairs On the next flap write: Multiple Alleles traits can be determined by more than just two alleles.
ex: blood type multiple genes determine the phenotype of trait or one trait can be affected by multiple genes.
ex. skin color, eye color, height in humans Polygenic Inheritance On the last flap write: Lesson 3 DNA & Mutants Genes provide the instructions for a cell to make molecules that express traits like your eye color, what kind of body build you should have, how big of a chin or nose you should have. DNA & Mutants These genes are sections of chromosomes.
Chromosomes are made up of proteins and deoxyribonucleic (dee AHK sih ri boh noo klee ihk) acid or DNA. DNA is an organism's genetic material. The Human Recipe Book Genes are like the specific recipes in the book while the DNA itself is the instructions. The entirety of the DNA code is made up of only four nucleotides. They are repeated and replicated over an over in different orders in a structure called a double helix. These nucleotides are like the alphabet of DNA.
guanine (G) They fit together like a puzzle with adenine or A's only connecting to thymine or T's. Cytosine or C's will only pair up with guanine or G's. This long stream of instructions lets a cell... know how and what to build. When a cell needs to divide to make a new cell, it makes new components including more DNA. During the process of replication the double helix of the DNA zips open and splits apart like a zipper and replicates itself. Replication It can do this because each side of the DNA has a special code. Remember A's only connect to T's, and C's only connect to G's. Mutation Your Recipe Book Title: The Human Recipe Book
Inside left: Genes are like the of the name recipe you want to make.
DNA is the specific instructions on how to make it.
On the right page: The alphabet of DNA is made up of only 4 nucleotides: A, T, C, G
A = adenine, C = cytosine, T = thymine ,
G = guanine Let's Make A Chain A mutation is a change in the nucleotide sequence of a gene. Mutation Sometimes mistakes are made. Most of the time these mistakes will be fixed or repaired before the DNA seals itself up. But sometimes mutations are made. Often mutations are not harmful. Sometimes they can benefit an organism. But in some cases they can be detrimental. If a mutation occurs in a sex cell, a cell that will produce a new offspring, then these traits will be passed on. Sometimes a new offspring with the new mutated DNA cannot survive and quickly dies after replication begins. Sometimes these negative mutations can result in genetic disorders. Cystic fibrosis: a defective gene causes mucus build up Williams syndrome: deletion of genes causes individuals to have developmental delays, facial differences, and cheery demeanor. These individuals are at ease with strangers. Down syndrome: additional chromosome either part or all of the 21 chromosome causing mental retardation and sometimes also restrictions on physical growth. Sickle-cell anemia: recessive blood disorder, oddly shaped blood cells have a limited capacity to carry oxygen and nutrients in the body. Individuals usually have a limited life span. Lesson 4 So how do we get all this DNA anyhow? So how do we get all of this DNA anyhow? As humans we get it from inheritance from our parents. Inheritance: the passing of traits from generation to generation. All of your inherited traits come from a combination of genes from your mother and father. This is done through a gene exchange known as sexual reproduction for many organisms like humans, plants, animals, etc. and through asexual reproduction. In sexual reproduction, chromosomes mix and match the traits they have. Then they split to make sex cells that have a mix of genetic material ready to donate half of an individual. Acquired traits are a bit different.
Acquired traits involve the environmental effects on an organism. Once people use to think that traits were acquired and could be passed down to their children. An acquired trait is a trait that is developed in an organism's lifetime and therefore is not inherited by the offspring. Acquired vs Inherited blue hair
sense of humor
ability to play volleyball
ADHD Lesson 5 Mitosis & Meiosis Mitosis a process during which the nucleus and its contents divide creating two genetically identical cells. Mitosis is useful for:
development and growth
and some asexual organisms reproduction Without mitosis your hair wouldn't grow, you'd have no new blood, in fact you would have never made it past a fertilized egg. 4 Phases of Mitosis Prophase Nuclear membrane breaks apart
Chromosomes condense and form like pairs #1 #2 4 Phases of Mitosis Metaphase like chromosomes line up along the center of the cell
Spindle fibers attach to each chromosome 4 Phases of Mitosis #3 Anaphase like chromosomes separate and are pulled to opposite ends of the cell. 4 Phases of Mitosis #4 Telophase Nuclear membrane forms around each set of chromosomes.
The cytoplasm divides, forming two daughter cells (or in plants a cell wall forms) Meiosis Your task... divide up into 4 groups
use the tune of a song you already know
write lyrics to describe the 4 phases of mitosis
write down the notes on paper
perform it for the class ...makes another me Meiosis is the process in which one diploid cell (a cell with pairs of chromosomes) divides to make four haploid cells (cells with half a set of chromosomes). This occurs only in the sex cells.
This occurs in phases similar to mitosis. But the cells divide twice and produce four daughter cells instead of two. Compare Mitosis and Meiosis Characteristics Mitosis Meiosis Number of chromosomes in parent cell
Type of parent cell
Number of divisions of nucleus
Number of daughter cells produced
Chromosome number in daughter cells
or pairs of chromosomes diploid or pairs of chromosomes reproductive/sex cells body 1 2 2 4 diploid or
pairs of chromosomes haploid or
half of a pair of chromosomes growth, cell repair, some types of reproduction forms sperm and egg cells Lesson 6 Sexual Reproduction Sexual Reproduction Sexual Reproduction is a type of reproduction in which the genetic materials from two different cells combine, producing an offspring. Advantages of Sexual Reproduction 1. Genetic Variation – individuals are genetically unique with slight variations.
These variations could be an advantage to fight off disease and evolve.
Ex. sickle cell anemia
2. Breeding – helps to produce plants or animals with specifically desired traits.
Ex. The selective breeding of grasses is what has given us the corn we eat today. Disadvantages 1. takes time and energy
waiting until maturity
can't have offspring if you can't find a mate
2. Possible exposure to sexually transmitted diseases
3. Fertilization cannot take place during pregnancy involves specialized sex cells
union of a female and male individuals or parts Sexual Reproduction Involves During the sexual reproduction process, genes swap alleles and the cell divides through meiosis to become four unique specialized sex cells. Haploid cells have half of the chromosomes or just one chromosome from each pair. In meiosis,
1 diploid cell (a cell with 2 sets of chromosomes one from each parent) splits to create 4 haploid cells. What kinds of organisms have sexual reproduction? Mosses Begins with either a male plant or female plant; Male produces sperm - Female produces an egg
When it rains the male plant releases its sperm and the sperm either splashes onto the female plant or it has to swim to the female plant to fertilize the eggs. After fertilization this produces a sporophyte which grows thousands of spores which are released in the wind and will germinate when it lands on the soil. Ferns They do not have seeds, but they do have spores. The gametophyte of the fern produces both eggs and sperm cells in one plant. Like the mosses the sperm is released during rain storm and swims to nearby eggs to fertilize them. Ferns When this occurs the plant grows into the fern plant and produces spores that burst and spread to new soils to start the cycle again. Grasses – bamboo, your lawn, wheat plants or corn plants, have a male and female parts as well. The male pollen relies on the wind to get it to the ovules (like eggs) to be fertilized. Cones from conifers or gymnosperms also rely on the winds to carry their pollen to the female parts of other trees. Because of this reliance on chance, these plants that use the wind to fertilize their offspring tend to need to produce tons of pollen just to ensure that their eggs become fertile. Flowers
Also have pollen and sexual reproduction, but flowers communicate with animals and lure them in with a tasty treat. The insect or animal gets nourishment and the planet gets pollination. Because the animals come to them, they don't need to take all the energy producing so much pollen.
Once fertilized, the plant will produce seeds. Animals that need to fertilized their eggs in water will tend to have an external sexual experience such as frogs, fish, coral, etc. The female will lay her eggs in the water and the male will excrete swimming sperm to fertile them. Sexual Reproduction Most animals (sperm and egg) Animals that do not go to the water like birds, mammals, some insects, etc. use an internal fertilization where a male body part will enter the female (in most cases) and inject sperm into the female
which swims to the
egg for fertilization. Animals & Sexual Reproduction Types of Organisms that do Sexual Reproduction: Plants Insects Flowers Animals Trees Conifers Mosses Ferns Lesson 7 Asexual Reproduction In sexual reproduction, an offspring inherits half of their DNA from each parent resulting in genetic variation- difference. Asexual reproduction one parent organism produces offspring without meiosis and fertilization. Because they inherit ALL of their DNA from just one parent, they are genetically identical to each other and to their parent. They are essentially clones or replications. Time to make another graphic organizer! This time just draw it in. Types of Asexual Reproduction fission: cell division in prokaryotes that forms two genetically identical cells. Mitotic cell division: eukaryotes reproducing from mitotic cell division. Budding: a new organism grows by mitosis and cell division on the body of its parent. animal regeneration: an offspring grows from a piece of its parent; also production of new parts. vegetative reproduction: a form of asexual reproduction in which offspring grow form a part of a parent plant. cloning: is a type of asexual reproduction performed in a laboratory that produces identical individuals from a cell or from a cluster of cells taken from a multicellular organism. Asexual Reproduction
reproduction without finding a mate
reproduce rapidly and large number of offspring Disadvantages
offspring are genetically identical to their parent (lower survival rate)
genetic changes or mutations can be passed on to every offspring Bacteria – some can divide and replicate once every 9.8 minutes. Fungus – can produce both asexual and sexual spores; asexual spores are pieces of the fungus that drop of or are ejected off from the reproductive sections of the fungus are carried off by the wind and become a genetically identical new offspring; hydra – live in unpolluted fresh water places like ponds and lakes. Interesting because they appear not to age or die due to their regenerative ability. They grow buds that grow into miniature adults. Then they break away and become a genetically identically new offspring. cuttings from some plants - Vegetative regeneration Rare animal asexual reproductions Organisms that have asexual reproduction:
amoeba (mitotic cell division)
fungus (vegetative regeneration)
sea stars (animal regeneration) Checkered whiptail lizard is an all female species of lizard that can lay eggs and produce viable genetically identical offspring. A couple types of stick-bugs are asexual producing eggs which hatch into genetically identical female offspring to that of the mother. Honey Bees - Drones are male honey bees. They develop from eggs that have not been fertilized, and they cannot sting, since the worker bee's stinger is a modified ovipositor (an egg laying organ).; Drones carry only one type of allele because they are haploid (containing only one set of chromosomes from the mother. -Wikipedia