12. Mutations and gene pools

Question 1

what is a species?

Answer 1

a group of individuals that share many characteristics and are able to interbreed under natural conditions to produce fertile offspring

Question 2

What are alleles?

Answer 2

alternative forms of a gene which determine the characteristics of an individual

Question 3

What is a population?

Answer 3

a group of organisms of the same species living together in a particular place at a particular time

Question 4

What are geneticists?

Answer 4

scientists who specialise in the study of inheritance

Question 5

What is a gene pool?

Answer 5

the sum of all the alleles in a given population

Question 6

What are allele frequencies?

Answer 6

how often each allele of a gene occurs in the gene pool for that population

Question 7

why do the frequency of particular alleles in a population?

Answer 7

due to chance events (mutation that alters the expression of a gene) or natural events (changes in the environment may result in variations of the allele frequencies)

Question 8

how can someone tell a mutation has occurred?

Answer 8

when an offspring shows variation that do not resemble either parent and have never occurred before

Question 9

what is a mutant?

Answer 9

an organism with a characteristic resulting from a mutagen

Question 10

what are the two types of mutations?

Answer 10

gene mutations and chromosomal mutations

Question 11

What is a gene mutation?

Answer 11

changes in a single gene so that traits normally produced by the gene are changed or destroyed

Question 12

What are chromosomal mutations?

Answer 12

all or part of a chromosome is affected

Question 13

When do gene mutations occur?

Answer 13

during the replication of the DNA molecule before cell division

Question 14

how is a mutation passed on from generation to generation?

Answer 14

when a cell divides, genetic information is usually passed on correctly
if a mistake occurs it will be faithfully be copied each time the DNA molecule replicates
hence the mutation is passed on from generation to generation

Question 15

what are mutagens/ mutagenic agents?

Answer 15

agents that increase the rate at which mutations occur

Question 16

what is a somatic mutation?

Answer 16

only the individual with the somatic mutation is affected

Question 17

why are somatic mutations not passed down?

Answer 17

mutation is passed onto daughter cells
reproductive cells aren’t affected and once the individual dies, mutation is lost
somatic mutations are involved in many cancerous growths that may be a result of a mutagenic agent

Question 18

what is a germinal/ germ-line mutation?

Answer 18

if reproductive cells are affected, the mutation may occur in the gametes and can be passed onto the subsequent generation

Question 19

does a germinal mutation affect the individual in which the mutation occurs?

Answer 19

no they aren’t usually affected, the individual just produces gametes with changed DNA
however the embryo is usually naturally aborted in early pregnancy

Question 20

what is a point mutation?

Answer 20

a change in just one base, could alter a protein, have no effect at all, or prevent the protein from being produced
if DNA of a particular gene is altered, the protein for which it codes for may be missing or abnormal

Question 21

what type of mutation is albinism?

Answer 21

point mutation

result of one missed protein, it is marked by an absence of pigment from hair skin and eyes

Question 22

what type of mutation is duchenne and how does it occur?

Answer 22

form of muscular dystrophy, is a gene mutation through the mother which is inherited by her sons

• also occurs in a male zygote so the child develops the disease
• disease results in a wasting of the leg muscles, arms, shoulders, and chest

Question 23

what type of mutation is cystic fibrosis?

Answer 23

gene mutation on a huge gene on chromosome 7
- gene codes for 1480 amino acids that make up a protein that regulates the passage of chloride ions across the cell membrane
mutant allele is recessive so to suffer from it, a person must inherit the mutant allele from both parents

Question 24

what are the types of chromosomal mutations?

Answer 24

deletion
duplication
inversion
translocation
non-disjunction

Question 25

what is a deletion in chromosomal mutations?

Answer 25

part of a chromosome is lost

Question 26

What is a duplication in chromosomal mutations?

Answer 26

a section of the chromosome occurs twice, this may happen if part of a chromatid breaks off and joins on the wrong chromatid

Question 27

What occurs in an inversion in a chromosomal mutation?

Answer 27

breaks occur in a chromosome and the broken piece joins back in, but the wrong way around
-this changes the order of genes on the chromosome and may disrupt the pairing of homologous chromosomes during meiosis

Question 28

what occurs in a translocation of a chromosomal mutation?

Answer 28

part of a chromosome breaks off and is rejoined to the wrong chromosome

Question 29

what occurs in a non-disjunction mutation of a chromosomal mutation?

Answer 29

during meiosis, a chromosome pair does not separate and so one extra daughter cell has an extra chromosome and one daughter cell has less than normal

Question 30

what occurs in the mutation for down syndrome (trisomy 21)

Answer 30

a child has 3 chromosome 21’s

a result of non-disjunction, the failure of one or more chromatids to separate in the second division of meiosis

Question 31

What is a partial trisomy?

Answer 31

when an individual has part of an extra copy of chromosome 21 (eg) which is attached to one of the other chromosomes

Question 32

what mutation occurs in patau syndrome?

Answer 32

trisomy 13 produces individuals with mental retardation, a small head, an extra finger on each hand, a cleft palate/lip and malformations of the ears and eyes
extra chromosome can either come from mothers egg of fathers sperm

Question 33

what mutation occurs in klinefelters syndrome?

Answer 33

males- non disjunction during either first or second meotic division
produces individuals with either an extra X chromosome (XXY) or extra Y chromosome (XYY)
develops as adults
they have small testes, dont produce sperm, breasts are enlarged and body hair is sparce

Question 34

what is a monosomy?

Answer 34

where an individual is missing a chromosome- only have one copy instead of 2

Question 35

What occurs if an autosome is completely missing?

Answer 35

monosomy results in severe malformations and miscarriages

Question 36

What happens in Cri-Du-Chat?

Answer 36

a rare genetic disorder due to a missing portion of chromosome 5
characteristics include a childs cry sounding like the meow of a cat due to problems with their larynx and nervous system

Question 37

What does turners syndrome produce?

Answer 37

females that are short in stature, lack secondary sex characteristics and are infertile
frequently diagnosed before birth by analysing cells in the amniotic fluid or placenta