Inheritance

Question 1

What is it meant by genetics?

Answer 1

the study of mechanisms by which an organism inherits characteristics from its parents.

Question 2

What is gene?

Answer 2

A length of DNA that codes for one polypeptide

Question 3

What is a locus?

Answer 3

the location of gene on chromosome

Question 4

What are alleles?

Answer 4

one version of particular gene

Question 5

What is dominant alleles?

Answer 5

• Presented as a capital letter
• the one that always produces an effect on the phenotype of organism when present

Question 6

What is a recessive allele?

Answer 6

• presented as a lower case letter
• the allele produces an effect on the phenotype only when present as an identical pair

Question 7

What is a genotype?

Answer 7

combination of alleles found in an individual

Question 8

What is a phenotype?

Answer 8

appearance of an organism
( determined by phenotype )

Question 9

What is it meant by homozygous?

Answer 9

• a pair of homologous chromosomes carrying the same alleles for a single gene

Question 10

What is it meant by heterozygous?

Answer 10

• a pair of homologous chromosomes carrying two different alleles for a single gene.

Question 11

What is F1 and F2 genotype?

Answer 11

F1 - first generation of offspring from genetic cross

F2 - second generation of offspring from genetic cross

Question 12

What are sex chromosomes?

Answer 12

carry genes that control whether an individual develops male or female reproductive systems

Question 13

What is it meant by codominant?

Answer 13

• both alleles are equally dominant and expressed in the phenotype.
• in exam more than 2 phenotypes

Question 14

What are multiple alleles?

Answer 14

• more than two alleles for a single gene
• more than 2 phenotypes

Question 15

What is a sex linkage?

Answer 15

• an allele is located on one of the sex chromosomes.
• its expression depends on the sex of the individual

Question 16

What is a autosomal linkage?

Answer 16

Genes that are located on the same chromosomes ( not the sex chromosomes)

Question 17

What is a monohybrid?

Answer 17

• genetic inheritance cross of a characteristic determined by one gene
• can identify in exam by 2 genotypes.

Question 18

What is a dihybrid?

Answer 18

• Genetic inheritance cross for a characteristic determined by two genes.

Question 19

What is Mendels first law of inheritance?

Answer 19

• law of segregation
• alleles separate randomly into gametes
• each parent passes one allele to their offspring

Question 20

what is Mendels second law of inheritance?

Answer 20

• law of independent assortment
• the alleles of genes assort independently of other genes during gamete formation

Question 21

define dihybrid inheritance

Answer 21

the determination of a trait by the inheritance of two genes

Question 22

what does mendelian inheritance assume?

Answer 22

• it assumes that the genes involved are not linked

Question 23

what is the chi squared test?

Answer 23

• a statistical test used to determine whether the difference between observed and expected data is due to chance or real effect

Question 24

what does it mean if the null hypothesis is rejected?

Answer 24

• there is a significant difference between the observed and expected results

Question 25

what is a mutation?

Answer 25

- the change is DNA arrangement or structure - may affect a single gene or whole chromosome.

Question 26

when do most mutations occur?

Answer 26

- crossing over in prophase 1 - non disjunction in anaphase 1 and 11

Question 27

what is a gene mutation?

Answer 27

- a change to at least one nucleotide base in DNA or the arrangement of bases - may occur spontaneously during DNA replication and can be beneficial, damaging or neutral

Question 28

give an example of a condition from gene mutation

Answer 28

- sickle cell anaemia

Question 29

describe sickle cell anaemia

Answer 29

- recessive genetic disorder caused by a substitution mutation on chromosome 11 - results in abnormal haemoglobin which distorts red blood cells

Question 30

what is a chromosome mutation?

Answer 30

a change in the structure or number of chromosomes, affecting many genes

Question 31

give an example of a condition that is caused by chromosome mutation

Answer 31

- downs syndrome

Question 32

describe downs syndrome

Answer 32

- due to non disjunction, an affected individual possesses three copies of chromosome 21

Question 33

what is chromosome non disjunction?

Answer 33

- failure of homologous chromosomes to separate in meiosis 1 or sister chromatids to separate in meiosis 11 - results in gametes with one extra or one less chromosome

Question 34

what is a mutagen?

Answer 34

- a chemical or biological agent that increases the rate of gene mutations above normal level

Question 35

give some examples of mutagens

Answer 35

- ionising radiation i.e X rays - chemicals ( polycyclic hydrocarbons )

Question 36

what is a carcinogen?

Answer 36

- a type of mutagen that causes cancer

Question 37

what is an oncogene?

Answer 37

- mutations of proto - oncogenes that are activated continuously, resulting in uncontrolled cell division

Question 38

what is a tumour supressor gene?

Answer 38

- slow down cell division

Question 39

define epigenetics

Answer 39

the study of changes in gene expression that are not due to alterations in the nucleotide of base sequence in DNA

Question 40

how can histone modification affect gene expression?

Answer 40

- alteration of histones by the addition of methyl, acetyl or phosphate group - increases or decreases gene expression by causing the histone to coil more tightly or loosely

Question 41

How can DNA methylation affect the gene expression?

Answer 41

- addition of methyl group to cytosine bases - prevents recognition of the bases, reducing gene expression