17 Inheritance

Question 1

What is a gene

Answer 1

A length of DNA, sequence of nucleotide bases, that normally code for a particular polypeptide

Question 2

How many alleles of a gene can occur at the locus

Answer 2

Only one allele of a gene can occur at the locus of any one chromosome
However in diploid organisms the chromosomes occur in pairs called homologous pairs, so two loci that each carry one allele of a gene

Question 3

Pair of homologous chromosomes showing diff possible pairings of dominant and recessive alleles

Answer 3

INSERT PIC

SEE TXTBOOK PG 155

Question 4

Summary of genotypes

Answer 4

INSERT PIC

SEE TEXTBOOK PG 156

Question 5

How to represent genetic crosses

Answer 5

INSERT PIC

SEE TXTBOOK PG 157

Question 6

Monohybrid inheritance

Answer 6

Inheritance of a single gene

Question 7

The law of segregation

Answer 7

In diploid organisms, characteristics are determined by alleles that occur in pairs
Only one of each pair of alleles can be present in a single gamete

Question 8

What is ratio

Answer 8

Measure of relative size of two classes that is expressed as a proportion

Question 9

Why is actual not same as expected

Answer 9

Discrepancy due to statistical error
It is chance that determines which gametes fuse with which
Larger sample more likely to produce actual results near theoretical ones, more representative

Question 10

Genetic cross for pure breeding

Answer 10

See card 1

Question 11

Genetic explanation of Mendals intercross between plants of F1 generation

Answer 11

See card 2

Question 12

Law of independent assortment

Answer 12

Each member of a pair of alleles may combine randomly with either of another pair

Question 13

Multiple alleles

Answer 13

Where there are more than two alleles of which only two may be present at loci of individual’s homologous chromosomes

Question 14

For codominant alleles how are letters written

Answer 14

See card 3

Question 15

Inheritance of ABO blood groups

Answer 15

Three alleles associated with gene I (immunoglobulin gene), which lead to presence of different antigens on cell surface membrane of red blood cells:
See card 4

Question 16

How many alleles present at one time

Answer 16

Although there may be three alleles e.g. ABO blood groups, only two can be present in individual at one time as there are only two homologous chromosomes and so only two gene loci

Question 17

Comparison of gametes produced by organism that is heterozygous for 2 genes A and B when they are linked and not linked

Answer 17

INSERT PIC

SEE TXTBOOK PG 437

Question 18

Example of autosomal linkage

Answer 18

See card 5

Question 19

Example of epistasis

Answer 19

See card 5

Question 20

Other forms of epistasis

Answer 20

Where genes act in sequence by determining enzymes in biochemical pathway
See card 6

Question 21

Chi2 test used to

Answer 21

It’s used to test null hypothesis

Question 22

Chi2 test can be used if certain criteria are met:

Answer 22

The sample size is relatively large, over 20.
Data must fall into discrete categories.
Only raw counts and not percentages, rates etc. can be used
It is used to compare experimental results with theoretical ones e.g. in genetic crosses with Mendelian ratios

Question 23

What are degrees of freedom

Answer 23

Number of classes - 1

Question 24

How to analyse calculated value for chi squared

Answer 24

Critical value is p= 0.05
If probability that the deviation is due to chance is equal to or greater than 0.05, deviation not significant, null hypothesis accepted.
If deviation is less that 0.05, deviation is significant, factor other than chance affecting results, null hypothesis rejected.