Chapter 9

Question 1

Define genetic mutation

Answer 1

A change in base sequence of chromosomes

Question 2

What are mutagenic agents? - give 2 examples

Answer 2

Agents that increase the amount of genetic mutation that occurs
Carcinogens
Radiation

Question 3

What are the 2 types of gene mutation?

Answer 3

Deletion

Substitution

Question 4

Why might a gene mutation not affect a protein?

Answer 4

Because the genetic code is degenerate a substitution might not cause a change in amino acid because some amino acids are coded for by more than 1 triplet so it is possible the amino acid will remain the same

Question 5

Define chromosome mutations

Answer 5

Changes in the structure or number of whole chromosomes

Question 6

What is Polyploidy?

Answer 6

A condition in which organsims have 3 or more whole sets of chromosomes rather than 2

Question 7

What is non disjunction?

Answer 7

A conditional where there is a change in the number of individual chromosomes where gametes have 1 more or less chromosomes than they should and therefore the cells have 1 more or less chromosomes than they should

Question 8

Define substitution

Answer 8

A type of gene mutation in which a nucleotide in a DNA molecule is replaced by another nucleotide thay has a different base

Question 9

Define deletion

Answer 9

A generic mutation that occurs when a nucleotide is lost from the normal sequence of DNA

Question 10

Why does deletion cause such an impact?

Answer 10

Because all triplets following the deletion will be impacted because the sequence of bases is read in groups of 3 bases

Question 11

What is meiosis used to make?

Answer 11

Gametes only

Question 12

Are cells made by meiosis haploid or diploid?

Answer 12

Haploid

Question 13

How many daughter cells are produced by meiosis?

Answer 13

4

Question 14

Does meiosis make genetically identical or genetically diverse cells?

Answer 14

Genetically diverse

Question 15

Meiosis can be described as a source of

Answer 15

Variation

Question 16

What stages are involved in meioisis?

Answer 16

Replication of genetic information in interphase
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

Question 17

What happens in prophase 1?

Answer 17

Chromosomes condense and are seen as 2 chromatids
The maternal and paternal chromosomes come together to form a homologous pair
Crossing over occurs
The nucleolus disappears and the nuclear envelope breaks down

Question 18

What happens in metaphase 1?

Answer 18

The homologous pairs of chromosomes line up on the equator of the spindle
Independent segregation is set up

Question 19

What happens in anaphase 1?

Answer 19

Independent segregation occues
The homologous chromosomes (1 from each bivalent) separate to each pole
Each pole receives a haploid number of chromosomes (2cells)

Question 20

What happens at telophase 1?

Answer 20

The chromsomes arrive at each pole 23 chromosomes at each

Temporarily the nuclear envelope forms again and cytokinesis occurs to make 2 cells

Question 21

What happens at prophase 2?

Answer 21

The nuclear envelope breaks down and new spindle fibres develope

Question 22

What happens at metaphase 2?

Answer 22

ChromoSOMES line up on the equator of the spindle fibre at the centromere and independent segregation is set up

Question 23

What happens at anaphase 2?

Answer 23

The centromeres divide and the chromATIDS are we pulled apart as separate pieces

Question 24

What happens at telophase 2?

Answer 24

The chromATIDS arrive at poles and lengthen to become indistinct
The nuclear envelope reforms
The spindle disappears
Cytokinesis occurs to make 4 haploid cells with 23 chromosomes each

Question 25

What are the 4 sources of variation in meiosis and fertilisation?

Answer 25

Crossing over Independent segregation Mutations Random fertilisation

Question 26

Define gametes

Answer 26

A mature haploid cell which is able to unite with another of the opposite sex to form a zygote

Question 27

Define homologous pair

Answer 27

A pair of chromosomes | 1 maternal and 1 paternal that have the same gene loci and therefore determine the same features

Question 28

Define crossing over

Answer 28

The process whereby a chromatid breaks during meiosis and rejoins to the a chromatid of the homologous pair so their alleles are exchanged

Question 29

Define independent segregation

Answer 29

Formation of random combinations of chromosomes in meiosis

Question 30

How do you calculate the number of possible chromosome pairs formed during independent segregation?

Answer 30

2 to the power of n

Question 31

Define genetic diversity

Answer 31

The number of different alleles of genes in a population

Question 32

Define species

Answer 32

A group if organisms with similar characteristics capable of interbreeding to produce fertile offspring

Question 33

Define population

Answer 33

A group of individuals of the same species in a habitat

Question 34

Explain the process of natural selection

Answer 34

1. random mutation or other sources of variation lead to new alleles which can cause selective advantage in the individual 2. this leads to increased rates of survival in the individuals 3. these individuals are more likely to successfully reproduce 4. this passes the advantageous allele on to the next generation 5. overtime the FREQUENCY OF THE ADVANTAGEOUS ALLELE INCREASES and the non-advantageous one decreases

Question 35

all organisms produce more offspring than ____ ___ _____ by the supply of food, light and space

Answer 35

can be supported

Question 36

despite overproduction of offspring most populations remain ______ . this suggests that there is ______ between members of a species

Answer 36

constant | competition

Question 37

within any population there is a wide variety of ______ in a gene _____

Answer 37

alleles | pool

Question 38

some organisms contain _____ that help them to _____ and ______. these organisms are more likely to pass on their _______ _____ to their offspring

Answer 38

alleles survive and reproduce advantageous alleles

Question 39

over time the ______ of the advantageous allele will ______ in a population and the non-advantageous allele will ______ in _____

Answer 39

frequency increase decrease frequency

Question 40

define selection

Answer 40

the process by which organisms that are better adapted to their environment tend to survive and reproduce while those that are less well adapted tend not to

Question 41

what are most characteristics described as?

Answer 41

polygenic (influenced by more than 1 gene)

Question 42

define directional selection

Answer 42

selection that favours an extreme phenotype over other phenotypes, causing the allele frequency to shift over time in the direction of that phenotype.

Question 43

give an example of directional selection

Answer 43

giraffes growing long necks

Question 44

when does directional selection occur? why?

Answer 44

when there is a change in the environment b/c the best adapted organisms survive and reproduce passing on the extreme alleles to their offspring so the next generation will show phenotypes that has shifted towards the extreme phenotype

Question 45

explain how antibiotic resistance of bacteria shows directional selection occuring

Answer 45

1. a spontaneous random mutation occurs in the allele of the bacterium and enabled it to make a new protein that was an enzyme 2. this enzyme was able to break down the antibiotic 3. the bacterium happened to be in a situation in which it was exposed to the antibiotic 4. the bacterium broke down the antibiotic so it survived but the rest died 5. there was no competition so the bacteria survived and reproduced by binary fission 6. the offspring inherited the ability to break down the antibiotic and there for the frequency of the allele increased in the population ad the normal distribution shifted to the direction of having greater resistance

Question 46

directional selection results in the _____ at one extreme being ____ for and the other extreme being ____ agains

Answer 46

phenotypes selected selected

Question 47

define stabilising selection

Answer 47

Stabilizing selection is any selective force or forces which push a population toward the average, or median trait.

Question 48

when does stabilising selection occur

Answer 48

when there is a stable environment

Question 49

give an example of stabilising selection

Answer 49

babies birth weight must be in the middle because if too high than there will be birthing complications and if too low the baby will be at risk once born