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Genetics: Heredity and Mutations

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Keystone Biology

on 20 October 2016

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Transcript of Genetics: Heredity and Mutations

Let's go on a treasure hunt for more information! See if you can find the buried treasure...
Review and Quiz!
Go to:
http://learn.genetics.utah.edu/content/basics/
Click through:
What is Heredity?, What is a Trait, What is a Chromosome?
Mendel- The Father of Modern Genetics
Gregor
Mendel
was a priest who worked in the garden of a monastery. As he bred pea plants, he noted important
patterns about how the traits
of the plants
were passed down
. Mendel came up with 3 important principles to sum up his findings.
Punnett Squares
The Punnett Square is a tool used to predict the
genotypes
and
phenotypes
of offspring. Punnett Squares have the parent gametes on the outside, and the products of fertilization are shown on the inside. This square only shows one trait, so it is for a
monohybrid
cross. These are probabilities, not guarantees.
Uncovering Inheritance Types
Your genetic inheritance is what you can pass along to the next generation or your offspring. There are several different types. Take a look below!
Understanding Chromosome Disorders
Chromosomal abnormalities, in the form of
non-disjunction
, are very common among humans.
Non-disjunction
occurs when chromosomes fail to separate evenly during either Meiosis I or Meiosis II. This results in the
incorrect
number of chromosomes being passed down to the offspring.

Three common categories of non-disjunction results crop up in humans:

Monosomy:
Occurs when one chromosome lacks its pair.
(Ex. Turner’s syndrome)

Trisomy:
Occurs when one extra copy of a chromosome is present. (Ex. Trisomy 21—Down’s syndrome…3 copies of the 21st chromosome)(Ex. Kleinfelters…3 copies of sex chromosomes)
• Polyploid:
Occurs when an entire extra set of chromosomes is present. This is fatal in animals, but fine for plants (Ex. Strawberries are Octoploid..they have 8 sets instead of 2)

Genetics: Heredity and Genetic Mutations
Key Vocabulary
• Alleles:
Alternative forms of a gene
• Autosomal chromosome:
A non-sex chromosome (X or Y are Sex Chromosomes)
• Chromosome:
A linear piece of DNA (X) that contains genes (or circular piece of DNA in bacteria)
• Diploid:
An organism with two copies of each chromosome
• DNA: DeoxyRibonucleic acid;
the molecule that carries genetic information
• Dominant:
An allele that completely masks the presence of the other recessive allele
• Gene:
The fundamental unit of heredity; a
specific section
of DNA within a chromosome
• Genotype:
The genetic makeup of an individual; the allele(s) at a given locus
• Heterozygote:
An individual with two different alleles of a given gene or locus
• Homozygote:
An individual with two identical alleles of a given gene or locus
• Locus:
A specific location on a chromosome
• Phenotype:
The physical characteristics of an individual
• Recessive:
An allele exhibited only when homozygous for 2 recessive alleles

Cystic fibrosis
Cystic fibrosis is an inherited disorder that mainly affects the lungs and pancreas. It is caused by a recessive allele. In a genetic diagram:
• the recessive allele can be shown as c
• the dominant allele can be shown as C

Someone who is homozygous (cc) for the recessive allele will develop cystic fibrosis. Someone who is heterozygous (Cc) or homozygous for the dominant allele (CC) will not develop cystic fibrosis.

Yellow vs. green peas
The
recessive allele
is represented by a
lower case
letter (for ex. y or t)
The
dominant allele
is represented by an
upper case
letter (for ex. Y or T)
Two
identical
copies of an allele is
homozygous
for that particular gene
Two
different alleles
for a particular gene is
heterozygous
for that gene
Can you fill in this tall vs. short square? Click on this link for more practice: http://www.sumanasinc.com/webcontent/animations/content/mendel/mendel.html
Mutations can involve an entire chromosome or a single nucleotide (just one of the A's, T's, C's or G's).
Germ cell mutations occur in an organism’s gametes (sperm or egg cells). These are the mutations that can be passed on and affect offspring. Somatic mutations happen in your body cells and are not passed on.
Excellent Work!
You found the buried treasure!
POINT ABNORMALITIES
Sometimes mutations occur on a much smaller scale that cause genetic disorders. Below is a list of genetic diseases.
Autosomal diseases
are not linked to a gender, they are on chromosomes 1-22.
Sex-linked traits
are found on the X chromosome and tend to be present more in males (who only have one X, and one Y, so they cannot mask a negative recessive trait with a second X).

Disease Type Effects
Sickle-cell anemia Autosomal recessive Changes blood cells; not
as good at picking up O2

Color-blindness Sex-linked Difficulty discerning
certain shades of colors

Huntington’s disease Autosomal dominant Degrades nerve cells,
leads to muscle &
cognitive problems
Point mutations:
when a single nucleotide mutates by being deleted, substituted or a nucleotided being added.
Substitution mutations:
happen when one nucleotide is replaced with another

• This can lead to a different codon which can lead to a different Amino acid & different shaped protein.
Frame Shift Mutation
The insertion or deletion of one or more nucleotides. Switches the order in which the codon’s are read and can be much more serious than a substitution.

DETECTING ABNORMALITIES
The use of
pedigrees
and
karyotypes
can be helpful in determining how a genetic disease is being passed down or if a person has a genetic disease.

Watch the video at:
http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/genesandinheritanceact.shtml

Take the quiz on BUZZ!
Let's begin! Follow me...
This is a long journey!
by O. Hipolit
Play this game!

http://learn.genetics.utah.edu/content/genetherapy/gtdoctor/
Single Gene Inheritance
Autosomal: t
he gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes).
X-linked (or sex linked)
: a gene that encodes for a particular trait is located on the X chromosome.
Dominant:
When one or both alleles is dominant the organism has the dominant trait.
Recessive:
When both alleles are homozygous with recessive alleles, it has the recessive trait.
Pleiotropy:
one gene can affect many traits in an organism such as a gene for blood cell shape which can effects blood flow, many tissues and organs, breathing, and overall health of the organism.
Multifactorial Inheritance
Multiple alleles:
More than two forms of a gene controlling the expression of a trait.
Polygenetic inheritance:
Single characteristic controlled by multiple genes.
Co-dominant:
When both alleles in a heterozygous organism contribute to phenotype. Both alleles are independently and equally expressed.
Incomplete dominance:
Neither allele is dominant nor recessive. Resulting offspring have a phenotype that is a blending of the parental traits.
Co-dominant
Incomplete dominance
Humans have 23 pairs of chromosomes including the 23rd pair which are the sex chromosomes
Karyotype
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