9. genetic diversity and adaptation

Question 1

what is a gene

Answer 1

length of DNA that codes for a polypeptides

Question 2

what is the locus

Answer 2

the position of a gene on the chromosomes

Question 3

what is a homologous chromosome

Answer 3

a pair of chromosomes that have the same gene at the same loci

(Different alleles)

Question 4

allele

Answer 4

a different form of a particular gene

Question 5

Describe frame shift. When does this happens

Answer 5

When triplets in a sequence of bases shifts to the left or right because of:

• addition of base
• deletion of base
• duplication of base

NOT substitution

Question 6

How does gene mutation effect an organism

Answer 6

If sequence of bases is changed than a different sequence of amino acids are put together, creating a protein with a different shape.

As proteins shape determines its function, a change in shape effects it’s ability to carry out its function.

Question 7

Describe what has happened when a directional selection is observed

Answer 7

Change in environment causes modal trait to change in response

Question 8

What are the two types of selection

Answer 8

• Directional
• Stabilising

Question 9

How do mitosis and meiosis differ

Answer 9

Meiosis
- TWO divisions
- HAPLOID cells are made
- introduced genetic VARIATION

mitosis
- ONE division
- DIPLOID cells are made
- create genetically IDENTICAL cells

Question 10

What is the diploid number in human?
what is the haploid number in humans

Answer 10

46
23

Question 11

Describe INDEPENDENT SEGREGATION

Answer 11

Two homologous chromosomes line up at equator

Which side each chromosomes are on are random

Pairs are separated

Large number of possible combinations in each daughter cell

Question 12

Describe CROSSING-OVER of chromosomes

Answer 12

Homologous pairs line up and become tangled and twisted around each-over

This causes part of the chromaTIDS to break off and attach to opposite chromosome

Resulting in a new combinations of alleles

Question 13

What three ways is variation introduced by meiosis

Answer 13

• Independent segregation
• Crossing over
• fertilisation is random (random sperm to egg)

Question 14

What is the formula for the possible chromosome combinations (involving meiosis)

Answer 14

(2n)^2
N = number of homologous pairs

Question 15

What two forms can chromosome mutations take?

Answer 15

• changes in the whole SETS of chromosomes. (polyploidy)
• changes in the number of individual chromosomes. (aneuploidy)

Question 16

What is meant by ‘non-disjunction’

Answer 16

homologous chromosomes fails to separate during meiosis. All are pulled to same side of cell.

Question 17

What is a mutagenic agent?

Answer 17

chemicals or radiation that increases likelihood of gene mutation by interfering with DNA replication

Question 18

What is polyploidy?

Answer 18

changes in whole sets of chromosomes, three or more sets rather than two. - common in plants, fatal for humans

Question 19

What is aneuploidy?

Answer 19

individual homologous pairs of chromosomes fail to separate during meiosis, resulting in more or fewer chromosomes

Question 20

When does independent segregation and crossing over take place?

Answer 20

• homologous pairs of chromosomes line up opposite each other at the equator.
• Distribution of paternal and maternal sides at the equator are random.
• results in many possible combinations of chromosomes in daughter cells

occurs during meiosis 1

Question 21

What is a diploid cell?
What is a haploid cell?

Answer 21

diploid, two full sets of chromosomes
haploid, one set of chromosomes

Question 22

What is a homologous chromosome?

Answer 22

a pair of chromosomes, one maternal and one paternal. - same gene loci

Question 23

Explain the process of meiosis

Answer 23

• first division (m1), = one chromosome from each pair into one of two daughter cells
• Second division (m2), chromatids move apart = 4 haploid cells.

Question 24

What is a zygote?

Answer 24

fertilized egg cell, fusion of sperm cell and ovum
- mitosis

Question 25

What is genetic diversity?

Answer 25

number of different alleles of genes in a population

Question 26

What does a population need for there to be natural selection?

Answer 26

genetic diversity

Question 27

Natural selection leads to…

Answer 27

evolution

Question 28

What is evolution

Answer 28

change in allele frequency over many generations.

Question 29

natural selection results in species becoming…

Answer 29

better adapted to their environment.

Question 30

Explain the process of natural selection

Answer 30

• new alleles from mutations
• allele increases an individual’s chance of survival = more likely to reproduce
• advantageous alleles passed on
• advantageous allele increases in frequency (over many generations)

Question 31

when modal trait changes towards one of the extremes ________ selection takes place.

Answer 31

directional

Question 32

Identify the two types of selection.

Answer 32

• stabilizing
• directional