Chapter 4 - Variation and mutation

Question 1

Phenotype

Answer 1

The observable form taken by a specific feature in an individual, based on genotype and influenced by environment

Question 2

Heredity

Answer 2

The transmission of traits from one generation to the next

Question 3

Variation

Answer 3

The diversity of genetic and phenotypic traits within and between populations

Question 4

Genotype

Answer 4

The genetic composition of an organism for a particular trait

Question 5

what are internal and external environmental factors

Answer 5

• External: temperature, pH, food availability. Eg, for crocodiles an embryo can become female or male depending on temperatures in the egg. Soil pH can affect flower colour in hydrangeas
• Internal: actions of hormones. Eg, Gonadotropin releasing hormone triggering the start of puberty in humans

Question 6

How can epigenetics affect phenotype, give example

Answer 6

By controlling gene expression. The addition of an acetyl group to promote transcription. the addition of a methyl group to reduce transcription. This does not change DNA sequence and therefore isnt a mutation

Question 7

How may mutations arise

Answer 7

• Spontaneously during DNA replication (spontaneous mutations)
• Induced by physical or chemical environmental factors (mutagens)
• Biological agents

Question 8

how is cancer caused

Answer 8

Mutation in a somatic cell that accelerate the rate of cell division affecting the cell’s ability to undergo apoptosis or increase the rate of mutations within the cell

Question 9

what is the difference between a mutation that produces a dominant allele and a recessive allele

Answer 9

Recessive mutations that lead to a loss of function can be masked if the normal copy of the gene is present, for the mutant phenotype to occur, both recessive alleles must contain the mutation. Dominant mutations lead to a mutant phenotype even in the presence of a normal copy

Question 10

aneuploidy

Answer 10

Describes a genome that varies from the conventional genomes through loss or addition of one or a few chromosomes

Question 11

Beneficial mutation

Answer 11

mutation that increases organisms chances of survival and reproduction

Question 12

Deleterious mutation

Answer 12

a mutation that decreases an organisms chances of survival and reproduction

Question 13

Deletion mutation

Answer 13

a mutation in which one or more nucleotide pairs have been lost from a segment of DNA, results in a frameshift

Question 14

double strand break

Answer 14

a mutation involving breaks in the sugar phosphate backbones of both DNA strands at the same nucleotide pair, resulting in the complete breakage of a chromosome

Question 15

Frameshift mutation

Answer 15

A mutation that changes the reading frame used in translation during polypeptide synthesis

Question 16

Insertion mutation

Answer 16

a mutation in which one or more nucleotide pairs have been added to a segment of DNA. resulting in a frameshift

Question 17

Missense mutation

Answer 17

A gene mutation that results in one amino acid being replaced by another amino acid in the encoded protein

Question 18

neutral mutation

Answer 18

A mutation that has no effect on an organisms chanced of survival and reproduction

Question 19

non disjunction

Answer 19

the failure of sister chromatids in mitosis or homologous chromosomes in meiosis to seperate and go to opposite poles

Question 20

nonsense mutation

Answer 20

a mutation in which a codon for an amino acid is changed to one that codes for a stop codon, terminating translation

Question 21

Point mutation

Answer 21

a mutation that affects a single base pair within a gene

Question 22

Polyploidy

Answer 22

a cell or organism with a genome comprising three or more copies of each chromosome (3n, 4n, 5n)

Question 23

spontaneous mutation

Answer 23

a mutation occurring in the absence of exposure to mutagens

Question 24

substitution mutation

Answer 24

a mutation in which a single nucleotide is swapped for another in the original gene sequence

Question 25

Synonymous mutation

Answer 25

a mutation in which the DNA codon for one amino acid becomes another DNA codon for the same amino acid

Question 26

what are the three Substitution mutations

Answer 26

Synonymous mutation (silent), Missense mutation, nonsense mutation

Question 27

parthenogenesis

Answer 27

A process in which an entire organism is a re-generated from a single egg cells

Question 28

What are the three types of point mutations

Answer 28

Substitution, insertion, deletion

Question 29

What are the four types of chromosomal mutation

Answer 29

Inversion, deletion, translocation, duplication

Question 30

Inversion mutation

Answer 30

Middle piece of a chromosome falls out, rotates 180º and the rejoins. reduced fertility

Question 31

Deletion chromosomal mutation

Answer 31

A region of a chromosome is lost, resulting in the absence of all the genes in that area.Eg williams syndrome

Question 32

Translocation mutation

Answer 32

The region from one chromosome is aberrantly attached to another chromosome. Eg when a segment of chromosome 8 ends up within chromosome 14 (vice versa), resulting in a form of cancer

Question 33

Duplication mutation

Answer 33

A region of a chromosome is repeated, resulting in an increase in copies of the genes in that region. Eg, genes that control different haemoglobin’s in RBC’s arise from duplications

Question 34

Independent assortment

Answer 34

The random orientation of maternal and paternal homologous chromosomes at the equator during metaphase one

Question 35

Random segregation

Answer 35

The phenomenon that starts during anaphase one, when the randomly lined up maternal and paternal homologous chromosomes move to opposite poles of the cell. Each gamete ends up with a random selection of maternal and paternal chromosomes

Question 36

Random fertilisation

Answer 36

The union of a male and female gamete, both haploid, which results in a diploid zygote. Is a random as there is no way of knowing which two gametes (each genetically unique) will form a zygote