Sex-linked ppt genetics

Genetics : 

Genetics Objectives: a) Review Mendelian Genetics b) Types of cells/Types of Chromosomes

Cells : 

Cells We have 2 types of cells 1. Somatic Cells (2n) – body cells 2. Sex Cells (n) – sperm and egg -Gametes

Chromosomes : 

Chromosomes We have 2 types of Chromosomes: 1. Autosomal chromosomes – pairs 1 through 22 in humans (non-sex chromososmes) 2. Sex chromosomes – xx or xy What about a fruit fly with a 2n = 8?

Sex-linked Traits : 

Sex-linked Traits

Definition : 

Definition Sex-linked traits are traits that are controlled by genes on the sex chromosomes The X and Y chromosomes

Are they controlled by both sex chromosomes? : 

Are they controlled by both sex chromosomes? Most sex-linked traits are controlled by genes on the X chromosome. This is because an X chromosome is much larger than a Y chromosome. A few traits are suspected to be controlled by genes on the Y chromosome, however there is less research about Y-linked traits.

Different Forms of Sex-linked Inheritance : 

Different Forms of Sex-linked Inheritance There are three different forms of sex-linked inheritance that we will be examining: X-linked recessive inheritance X-linked dominant inheritance Y-linked inheritance

X-linked Recessive Inheritance : 

X-linked Recessive Inheritance X-linked recessive traits are traits resulting from a recessive allele on the X chromosome. There are over 100 different human conditions that are caused by recessive alleles found on the X chromosomes. X-linked recessive alleles are represented by a X , superscript lower case letter or a plus/minus (+/-)

X-linked Recessive Inheritance : 

X-linked Recessive Inheritance These traits tend to show up in males more than females. Why? Because males only carry one X chromosome! ( they have one x chromosome, and one Y chromosome that make up their sex chromosomes).

X-linked Recessive Inheritance : 

X-linked Recessive Inheritance Example #1: Colorblindness The allele that controls colorblindness is found on the X chromosome and is recessive . What genotype must a female have to be diagnosed as colorblind? Homozygous recessive (X-X-)

Are you colorblind? : 

Are you colorblind? Normal Color Vision:A: 29, B: 45, C: --, D: 26 Red-Green Color-Blind:A: 70, B: --, C: 5, D: -- 3. Red Color-blind:A: 70, B: --, C: 5, D: 6 4. Green Color-Blind:A: 70, B: --, C: 5, D: 2

Try this problem! : 

Try this problem! What is the probability that the sons of a homozygous recessive mother would be colorblind? Represent colorblindness with a “-” Mothers Genotype X- X - Each son would receive an X chromosome from their mother which means… Each son would have an X chromosome with a recessive allele for colorblindness and would express the trait!

X-linked Recessive Inheritance : 

X-linked Recessive Inheritance Example #2: Hemophilia Hemophilia Hemophilia is a serious ailment in which the blood lacks a clotting factor, and therefore when an individual is injured, they cannot stop bleeding. Hemophilia is also controlled by recessive alleles on the X chromosome.

X-linked Dominant Inheritance : 

X-linked Dominant Inheritance X-linked dominant traits are traits that result from the presence of a dominant allele on the X chromosome. Unlike X-linked recessive traits, females and males both require only ONE dominant allele in order to express the trait. X-linked dominant traits are represented by an X, superscript capital letter or a (+)

Y-linked Inheritance : 

Y-linked Inheritance Do the words homozygous or heterozygous apply to Y-linked traits? Are females affected by Y-linked traits? No, because there is only ever one Y chromosome present at a time! No, because females don’t carry Y chromosomes!

What is this? : 

What is this?

Y-linked Inheritance : 

Y-linked Inheritance An example of a Y-linked trait is . . . . . HAIRY EARS!

Y-linked Inheritance : 

Y-linked Inheritance All of the sons of an affected male will display this Y-linked trait.