Unit: Human Genetics(Class Notes)
Chromosome - Each species has a
Number- Humans have
- Fruit flies have
- Turkeys have
- Where do we get them from?
- Gametes have (23)
-
- They come together during to give us
-
Chromosomes &- We have two types of chromosomes:
Sex Determination 1)
- all chromosomes other than sexchromosomes
- pairs
2)
- determine the sex of an individual
- only ___ pair
- could be X or Y
- female= ____
male= ____
Question: Who determines the sex of the baby? Male or female?
What are the chances a baby will be a boy or girl? (hint: punnett square)
Karyotype - A karyotype is a picture of
Process
1)Cells are during mitosis
2)The chromosomes are of the picture and put in
3)The pairs are put in order from
What do scientists look for?
•Are there 46 chromosomes?
•Are there 2 identical pairs of each autosome and 2 sex chromosomes?
•Are any chromosomes missing pieces or mixed up?
Uses
- to detect
- for counseling prospective parents
Sex-linked Trait - traits are traits coded for by
- Traits whose genes are located on sex-chromosomes are called
- Genes carried on the chromosomes =
- the Y chromosome is much than the X chromosome.
- It appears to contain only a.
- Sex-linked traits are more likely to bepassed on to than
- Why??
- Females have _____ X chromosomes
- Possible genotypes:
______, ______, ______
“normal” “carrier” “affected”
- carrier carries the gene but does not show the trait
()
- males have only _____ X chromosome
- Y chromosome does not carry many genes
- Possible genotypes:
______, ______
“normal” “affected”
- For a recessive allele to be expressed in females, they must have
(Ex: XhXh)
- Since males have just one X chromosome, all X-linked alleles are
expressed even if they are recessive (Ex: XhY)
Common 1) = cannot see some colors
Sex-linked
Genetic Disorders 2) = blood cannot clot dueto lack of
Sex-linked - Example 1:Colorblindness
Problems B = b =
XBXb x XBY
(carrier) (normal)
Example 2: Hemophilia
H = h =
XHXh x XhY
(carrier) (hemophiliac)
Mutation - Any change in the
- can be caused by factors such as
- Mutation can occur at two levels:
1)
2)
DNA/ Gene - involves changes in
Mutation
1) Mutation
- a change in a
Ex: Our big dog bit the man
2) Mutation
-
Ex: Our big dog bit the man
Addition:
Deletion:
Chromosome – involves changes in
Mutation
= a piece is lost
= a piece is duplicated
= a piece of a chromosome is reversed
= a broken pieceattaches to another
chromosome
= chromosomes fail to separate during meiosis
- Can result in:
Genetic Disorders 1) = One too few chromosomes
caused by - Example:
non-disjunction -
- Only
-
2) = one too many chromosomes
- Examples:
- Super Female ():
-
- Klinefelter Syndrome ( ):
- Usually the result of
-
-
- Down Syndrome ():
-
-
-
Pedigree Charts- A pedigree chart shows the
- Genetic counselors use pedigree charts to determine the
of family members
More Genetic - Genetic disorders can be caused by a
Disorders
- Recessive alleles:
- Phenotype expressed only by individuals
-
- Example:
- Cystic fibrosis
- trait
- Caused by a
- The
-
What are the genotypes of these individuals?
- Phenylketonuria (PKU)
- trait
- The defective gene codes for an
- As a result,
- Leads to
- Treatment involves a
- Tay-Sachs Disease
- trait
- The defective gene causes
- Nervous system breaks down
- Symptoms include
- Dominant alleles:
- Dominant alleles are expressed even when the recessive allele is
present
- Example:
- Huntington’s Disease
- trait
-
- Codominant alleles
- Both genes are expressed
- Example:
- Sickle Cell Disease
-
-
- Causes
- They get
- The heterozygous advantage:
- Individuals with both normal and sickle cells alleles
(heterozygous) are also
- Malaria is a disease caused by a
- In areas like Africa where Malaria is present,
heterozygotes have an advantage!
- They