Human genetics презентация

Human genetics
Determines how hereditary information is passed and observes these traits in individuals
Studies the relationship between hereditary information and the environment
Helps in treating genetic diseases
Human inheritance can be studied by pedigree analysis, population studies

Human genetics
The 46 chromosomes in human cells are found in 23 pairs.
44 are body chromosomes, or autosomes
The other two chromosome are sex chromosomes

According to the chromosome naming system of chromosomes are divided into 7 groups (A,B, C, D, E, F, G) based on their size and the position of their centromeres
Chromosomes

A pedigree is used to determine whether an individual is heterozygous or homozygous for a certain trait, and to calculate the possibility of exhibiting this trait in the phenotype
Pedigree (Family Tree)

Pedigrees are based on observation.
First statistical data is collected, and then laws of probability are applied to this data
Pedigrees are divided into 2 types:
- Autosomal
- Gonosomal
Pedigree (Family Tree)

Autosomal Pedigree - Related genes are located on autosomal chromosomes as dominant or recessive

Gonosomal Pedigree
Pedigree Based on Sex Chromosomes
They can be dominant or recessive.
While the genes located on only Y chromosomes can be seen only in males
The genes located on X chromosomes can be seen in both males and females

A man with a Y-linked disorder has three sons and three daughters by the same mother. His first son has two sons and two daughters by another woman. Draw the pedigree for this family

A man with a X-linked disorder has son and three daughters (2 of them are normal, one is a carrier) by the same normal mother. His first daughter has two sons (one of them is normal, another is ill) and one daughter (carrier) by another man. Draw the pedigree for this family

Sex-linked inheritance in human
In humans, inheritance is based on X,Y and XY chromosome linkage.
X-linked inheritance is seen only in females.
However Y and XY-linked inheritance affects both males and females.

X-Linked Inheritance
The effective genes are recessive and found on the X chromosome
Colorblindness (Daltonism) and hemophilia are examples of X-linked inheritance

Hemophilia is an inherited disease in which the blood clots very slowly or not at all
This disease is more lethal than colorblindness.
The gene for hemophilia is represented by “h” and the normal gene by “H”.
Hemophilia

A colorblind individual can not distinguish between red and green (Daltonism).
The gene for colorblindness is represented by “r”, while the gene for normal vision gene is represented by “R”
Because females have XX sex chromosomes, colorblindness can occur only if the colorblindness gene is homozygous.
Colorblindness

The characteristics of Y chromosome are only found on Y chromosome
For this reason, these characteristics are only seen in male
Ex: flatfoot and hairloss
Y-linked inheritance

Problem 1
A human female "carrier" who is heterozygous for the recessive, sex-linked trait causing red-green color blindness, marries a normal male.
What proportion of their male progeny will have red-green color blindness (or alternatively, will be daltonic)?
100%
B. 75%
C. 50%
D. 25%
E. 0%

Problem 2
A human female "carrier" who is heterozygous for the recessive, sex-linked trait red color blindness, marries a normal male.
What proportion of their female progeny will show the trait?
A. 1/2
B. 1/4
C. 0
D. 3/4
E. All

Problem 3
A human female "carrier" who is heterozygous for the recessive, sex-linked trait red color blindness, marries a normal male.
What proportion of their female progeny will show the trait?
A. 1/2
B. 1/4
C. 0
D. 3/4
E. All

Problem 4
Hypophosphatemia (vitamin D-resistant rickets) is inherited as an X-linked dominant. An unaffected woman mates with a male with hypophosphatemia. What is the expected phenotypic ratio of their offspring?

Problem 5
Hypophosphatemia (vitamin D-resistant rickets) is inherited as an X-linked dominant.
A woman without hypophosphatemia and a man with hypophosphatemia have a daughter.
The daughter mates with a male without hypophosphatemia.
What is the expected phenotypic ratio of their offspring?

Problem 6
A human female "carrier" who is heterozygous for the recessive, sex-linked trait red color blindness, marries a normal male.
What proportion of their female progeny will show the trait?
A. 1/2
B. 1/4
C. 0
D. 3/4
E. All