Genes And Patterns Of Inheritance

Question 1

What is a gene

Answer 1

A short length of DNA that codes for a polypeptide

Question 2

What does genetic locus refer to

Answer 2

The position of a gene on a chromosome

Question 3

What is an allele

Answer 3

An alternative form of a gene

Question 4

What is a genotype

Answer 4

Alleles present for particular trait

Eg eye colour

Question 5

What is the phenotype

Answer 5

The appearance of a trait

Eg blue eyes

Question 6

What is the definition of hereditary

Answer 6

Transfer genetic factors from one generation to the next

Question 7

What is mendels first law

Answer 7

When an individual produces gametes the alleles separate so that each gamers receives only one allele

Question 8

Describe monohybrid inheritance

Answer 8

1. Alleles separate when gametes are produced

2. Alleles combine at fertilisation when gametes fuse

Question 9

Describe codominance

Answer 9

Alleles interact to produce a heterozygote with its own distinctive phenotype
Red x white = pink

Question 10

Describe lethal allelic combinations

Answer 10

One allele in homozygous state causes death at early stage

Question 11

What does multiple alleles mean

Answer 11

More than 2 alleles for a gene

Question 12

Describe sex linkage

Answer 12

Gene and allele located in sex chromosome

Question 13

When is a test cross used

Answer 13

To establish the genotype of unknown organisms

Question 14

Describe a test cross

Answer 14

• Organism crossed with homozygous recessive

- because you can recognise it by its phenotype and it only passes in a recessive allele

Question 15

Describe the results of a test cross if the tested organism is heterozygous or homozygous

Answer 15

If homo - all dominant phenotype

If hetero - mix of dominant and recessive

Question 16

Describe co dominance

Answer 16

One allele does not completely dominate the other on a particular chromosome locus
2 alleles both expressing equally

Question 17

Describe partial dominance

Answer 17

Between shades of complete dominance and no dominance

Question 18

What do the offspring of co dominance look like in relation to parents

Answer 18

Look like neither parent

Intermediate between homozygous dominant and homozygous recessive

Question 19

Describe multiple alleles

Answer 19

More than 2 alleles of a particular gene exist

Only 2 present on loci of chromosome

Question 20

Describe a lethal allele

Answer 20

It stops producing a protein

Which prevents operation of a vital function

Question 21

What are the three forms of death a lethal allele can produce

Answer 21

Death of zygote - no evidence
Death after reduced lifespan
Death at early stage of development - presence of allele evident

Question 22

Describe x linked recessive traits (who are they inherited from)

Answer 22

Males inherit from female parent

Females must inherit from both parents

Question 23

Describe x linked dominant traits

Answer 23

Expression in both sexes 
Female can be homo or hetero
Male is hetero
Positive father gives to all daughters 
Positive mother gives to half sons and half daughters

Question 24

Describe sex linkage on the Y chromosome

Answer 24

Males inherit Y from father

Every son affected

Question 25

Describe autosomal inheritance

Answer 25

Trait appears to skip a generation

Question 26

Describe x linked recessive inheritance

Answer 26

Carrier mother gives trait to half of sons
Infected mother gives trait to all sons
For female to be infected the father must be infected

Question 27

Describe autosomal dominant inheritance

Answer 27

One parent must have trait

Equal number of male and female

Question 28

Describe x linked dominant inheritance

Answer 28

Not restricted to males

Question 29

What is epistasis

Answer 29

One gene interferes with the expression of another