3.4 INHERITANCE

Question 1

Dominant

Answer 1

allele that is expressed in the heterozygous

Question 2

Recessive

Answer 2

allele that is not expressed in the heterozygous

Question 3

Gametes

Answer 3

haploid sex cells formed by the process of meiosis
male → sperm
female → ova

Question 4

zygotes

Answer 4

when the male and female gametes fuse during fertilisation (contains two alleles for each gene)

Question 5

Heterozygous

Answer 5

when the allele in the genotype are not the same

Question 6

Homozygous

Answer 6

when the allele in the genotype are the same

Question 7

AA

Answer 7

Homozygous Dominant

Question 8

Aa

Answer 8

Heterozygous

Question 9

aa

Answer 9

Homozygous Recessive

Question 10

Genotype

Answer 10

the combination of alleles of a gene carried by an organism

Question 11

Phenotype

Answer 11

the expression of alleles of a gene carried by an organism

Question 12

Codominant alleles

Answer 12

alleles that are both expressed equally in the phenotype of a heterozygous individual

They therefore have an altered phenotype as the alleles are having a joint effect

Question 13

A and B blood Groups

Answer 13

co-dominant and each modify the structure of the antigen to produce different variants

Question 14

O blood group

Answer 14

recessive and does not modify the basic antigenic structure

Question 15

Type A

Answer 15

Anti-B Antibody

Cannot have B or AB Blood
Can have A or O blood

Question 16

Type B

Answer 16

Anti-A Antibody

Cannot have A or AB Blood
Can have B or O blood

Question 17

Type AB

Answer 17

Neither antibody

Can have any type of blood

Question 18

Type O

Answer 18

Both Antibodies

Can only have O blood

Question 19

Genetics disease

Answer 19

diseases caused by a gene

Question 20

Carriers

Answer 20

Heterozygous individuals will possess one copy of the faulty allele but not develop disease symptoms

Question 21

Autosomal recessive genetic disease

Answer 21

will only occur if both allele are faulty

Question 22

Autosomal dominant genetic disease

Answer 22

only requires one copy of a faulty allele to cause a disorder

Question 23

Sex linkage

Answer 23

when a gene controlling a characteristic is located on a sex chromosome

Question 24

Cystic Fibrosis

Answer 24

Autosomal recessive disorder

Mutation in chromosome 7

Produce mucus unusually sticky and thick

This mucus clogs the airway and secretory ducts of the digestive system → respiratory failure

Question 25

Huntington’s Disease

Answer 25

Autosomal dominant disorder

Mutation in chromosome 4

The HTT gene posses a repeating trinucleotide sequence (CAG) that is usually present in low amounts

+28 CAG repeats → unstable

+40 → the huntingtin protein will misfold and cause neurodegeneration

Symptoms →dementia and uncontrollable spasmodic movements

Question 26

PKU

Answer 26

a mis-sense mutation in the gene that produces tyrosine hydroxylase

phenylalanine cannot be converted to tyrosine so it builds up

resulting in brain developmental problems and seizures

Dairy, breastmilk, nuts are avoided since they are rich in phenylalanine

Question 27

Colour-blindness

Answer 27

an individual fails to discriminante between red and green hues

caused by a mutation to the red or green retinal photoreceptors, located in X-chromosome

XA → unaffected
Xa → affected

Question 28

Haemophilia

Answer 28

when the body’s ability yo control blood clotting is impaired

The formation of a blood clot is controlled by a cascade of coagulation factors whose genes are located on the X chromosome

When one of these factors becomes defective, fibrin formation is prevented - meaning bleeding continues for a long time

XH → unaffected
Xh → affected