Mendelian Genetics Flashcards Preview

Year 1 Biology Ellie M > Mendelian Genetics > Flashcards

Flashcards in Mendelian Genetics Deck (19):
1

What is Mendel’s first law?

Alternative versions of a gene account for variations in inherited characters

2

What is Mendel’s second law?

Each character is independently inherited during gamete formation - each pair of alleles of a given gene are independently inherited from alleles at a different gene locus

3

Causes of deviations from Mendelian ratios

Epistasis
Incomplete dominance
Co-dominance
Co-dominance and multiple alleles
Lethal alleles

4

What is the difference between co-dominance and incomplete dominance?

In co-dominance heterozygote expressed in both forms - offspring looks like both parents at once
Incomplete dominance the heterozygote forms an intermediate phenotype - looks like a blend of both parents

5

What is pleiotropy?

When one gene influences 2 or more phenotypic traits

6

What is allelic heterogeneity?

A similar phenotype produced by different alleles of the same gene

7

What is locus heterogeneity?

A similar phenotype is produced by mutations at different gene loci

8

What is incomplete penetrance?

Not all individuals carrying a deleterious gene express the associated trait

9

What is linkage?

When particular gene loci are inherited jointly

10

Who discovered linkage?

Bateson and Punnet
Soon after 1900

11

What is recombination frequency?

A measure of how often recombination occurs between genes, measured as the fraction of offspring that inherit recombinant proteins

12

What is recombination frequency measured in?

centiMorgans (cM)

13

How do recombination frequencies determine where genes are relative to each other on a chromosome?

Recombination is less likely between genes that are closer, because there is less DNA between them

14

Why don’t gene mapping recombination frequencies always add up to 100%?

Double crossing over can occur

15

What is another name for a sex chromosome?

Allosome

16

What is X inactivation?

The inactivation of one of the two copies of the X chromosome in all female mammals. Happens during embryonic development

17

What does the inactivated X chromosome become?

It condenses into a compact object called a Barr body. Most of its genes aren’t expressed and it lies alongside the nuclear envelope

18

Why does X-inactivation not cause colourblindness?

The X chromosome is inactivated on a cell-by-cell basis - any daughter cell from one of the original embryonic cells will have the same X chromosome inactivated. As the eye comes from several different cells, some will have one X chromosome inactivated whilst others will have the other one inactivated

19

How is mitochondrial DNA transcribed?

Like in prokaryotic cells with the production of polycistronic RNA (multiple genes on a single RNA molecule)