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Basics of Genetics
Transcript of Basics of Genetics
There are over a million species of organisms on earth.
A chromosome is an organized structure of DNA and protein that is found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences.
Chromosomes are usually in pairs. Humans have 23 pairs of chromosomes.
A karyotype is the number and appearance of chromosomes in the nucleus.
The term is also used for the complete set of chromosomes in a species, or an individual organism.
Karyotypes describe the number of chromosomes, and what they look like under a light microscope.
This is the human male karyotype
There are an equal number of copies of the chromosome in males and females. For example, in humans, there are 22 pairs of autosomes. In addition to autosomes, there are sex chromosomes, specifically: X and Y. So, humans have 23 pairs of chromosomes.
Female Fruit Fly Karyotype
Formation of New Cells
Meiosis is a special type of cell division necessary for sexual reproduction.
In animals, meiosis produces gametes like sperm and egg cells
Mitosis is the process by which a cell separates the chromosomes, in its cell nucleus, into two identical sets in two nuclei.
An autosome is a chromosome that is not a sex chromosome
DNA is a very long molecule that looks like a spiral ladder.
This structure is called the double helix.
It is made of repeating chemical units that contain specific “bases”.
There are 4 different bases in DNA called:
When 2 strands of DNA combine, C & G join together and A & T join together. This is called “base pairing”.
Each molecule of DNA is very long and has a sequence of A, T, G & C.
The sequence on the other strand is called the complementary sequence.
Write down the complementary sequence for:
A T T C G G C T A T A C G C
T A A G C C G A T A T G C G
Each DNA strand has hundreds of thousands of DNA bases.
The total amount of DNA including the genes of an organism is called the genome.
The DNA strand is broken up into sections called genes.
Humans have about 30,000 genes.
Genes carry the information for making all the proteins required by an organism.
The principle role of DNA is to instruct cells to make proteins.
Proteins are a family of large chemicals which are made from amino acids joining together.
Different proteins cause differences in appearance.
Genes determine what an organism looks like, how it functions and even how it behaves.
They do this because all organisms (except for identical twins) have unique genes that make unique proteins.
The proteins are unique because they are made from different amino acids or from amino acids being placed in a different order.
Did you get...
Where do amino acids come from?
Digestion breaks proteins down & separates all of the amino acids from the food.
Our bodies make many different proteins because they have specific jobs to do.
Amino acids come from proteins in food which are eaten and digested.
Cells in the body then join specific amino acids together to make different proteins.
The Genetic Code
The order of bases in a single strand of DNA instruct cells on which amino acids need to be joined together to make a particular protein.
The code uses 3 bases (a triplet) to code for each individual amino acid.
Some amino acids have more than one triplet code.
Which amino acids would be joined together by this sequence of DNA?
AAC GTA CGT
AAC GTA CGT
Did you get...
leucine histidine alanine
Functions of proteins:
Make up the “building material” of the body e.g hair, fingernails
This can be found on page 117 of your text
Mutations are what lead to variation in a species.
Mutations are changes that occur in the sequence of a gene and subsequently change the protein encoded by that gene.
They are usually harmful and cause genetic diseases but in some cases are beneficial.
Some mutations may not even change the protein and therefore have no impact on health.
Genetic Disorders are inherited conditions that are caused by faulty (mutated) genes.
Somatic mutations are changes to the genetics of an organism which are not passed on to its offspring through the germline.
Many cancers are somatic mutations
Genetics is the study of heredity...
Heredity is the study of biological inheritance ('handing down of genes' - the passing down of biological traits such as hair colour, skin type etc... )