Bio 120-Chromosomal Genetics

How the genes act in gene expression

Describe a pair of chromosomes carrying a same gene

Describe a pair of chromosomes carrying a same gene

• Chromosomes carry two alleles at the SAME POSITION

How do gametes separate the alleles ?

Each gamete will get one membre of the pair of the allele

Explain recombination of unlinked Genes in allele segregation

1. Chromosome will replicate ( two pairs of the same genes but maybe with different form i.e. TT and tt)

2. Homologous pairs will separate in two different cells(TT in one and tt in other)

3. Sister chromatids are now separated (now, T, T, t and t each in one cell

Explain recombination of unlinked Genes in independent assortment

Genes for two traits are on different genes (i.e the pair does not match

1. Chromosomes replicate (start with yR and Yr ) so homologous =yRyR and YrYr)

Who discovered that crossing over accounts for the recombinants ?

T.H. Morgan and his students in the 1900s

Which experiment did he conduct? Procedure

He used fruit flies to cross a homozygous dominant for both traits with a homozygous recessive for body colour (grey) and wings (straight)

1. With the F1 being heterozygous for both traits

2. Performed a text cross and expected a 1:1:1:1 like mendel

3. Was not that ratio

What’s another way to call the Map Unit?

centiMorgan

What was the conclusion of Morgan’s experiment?

Genes carried on the same chromosomes follow the mechanical basis of heredity

What determines the sex of te offspring in genetics?

The gamete from the male

• Females can only pass on the X chromosomes

• Males can pass on X chromosome or Y chromosomes

How are female’s sex chromosomes? Male’S sex chromosomes?

• Female: 22 pairs + XX

• Male: 22 pairs + XY

What is an autosome?

Any chromosome that is not a sex chromosomes

Between the X and Y chromosome, which carries the most genes?

X genes

Which sex do sex-linked recessive diseases affect more frequently?

The male sex

What is extranuclear Inheritance

When a gene is passed down by the female parent

What are some examples of genes passed down using extranuclear inheritance?

• mitochondria

• chloroplast

Explain how epigenetics affects the embryo’s formation?

The passing on of traits that are due to physical conditon, regardless of genetic makeup ( identity)

What are some cons about the extranuclear inheritance in mitochondria?

• High mutation rate

• Threshold effect of disease

• Age-related mutation ( older you get, the more the mutations within the mitochondrial gene

How are extranuclear inheritance passed down? mitochondria and chloroplast

Through maternal inheritance

What is a third type of Extranuclear inheritance?

By an infectious agent that mediates horizontal gene trasfer

How does horizontal gene transfer happen?

AN infectious agent transfers a pieace of their DNA and transfers it to a part of …