Meiosis and mutations

Question 1

What does diploid mean?

Answer 1

cells where the nucleus has two sets of chromosomes

Question 2

What does haploid mean?

Answer 2

cells that only have one copy of each chromosome

Question 3

What is a homologous pair?

Answer 3

a pair of chromosomes, one maternal and one paternal, that have the same gene loci and determine the same features

Question 4

What is meiosis?

Answer 4

the type of cell division where the number of chromosomes is halved- results in 4 non- genetically identical daughter cells

Question 5

What is a chromatid?

Answer 5

one of the arms of a chromosome

Question 6

What is a centromere?

Answer 6

joins the chromatids together to make a chromosome

Question 7

What is independent segregation?

Answer 7

randomly shuffled homologous pairs- each chromosome is inherited randomly, and independent of each other- inheritance of one does not impact inheritance of another

Question 8

What is recombination/crossing over?

Answer 8

happens when the chromatids of a bivalent get twisted, and breaks occur, meaning parts of the chromatids are exchanged between homologous pairs. it happens at random and is very rare/infrequent

Question 9

What is a mutation?

Answer 9

a change in the amount or structure of DNA

Question 10

What is acquired mutation?

Answer 10

occurs in cells after conception

Question 11

What is hereditary mutation?

Answer 11

a gene change in a gamete that becomes incorporated into the DNA in every cell of the body of the offspring

Question 12

What are the two types of mutation?

Answer 12

a gene mutation- a change in the base sequence of the gene, which can cause a change in the polypeptide chain. it is caused by errors during DNA replication

a chromosome mutation- a change in the number or structure of the chromosomes. it is caused by errors during cell division

Question 13

What is substitution?

Answer 13

when one of the bases is swapped for a different base- DOES NOT RESULT IN FRAME SHIFT- but could change the amino acid it codes for

Question 14

What is deletion?

Answer 14

the removal/deletion of a base in a sequence, causing a frame shift to the left

Question 15

What is addition?

Answer 15

the addition of a base in a sequence, causing frame shift to the right

Question 16

What is frame shift?

Answer 16

when, due to the addition or deletion of a base, the subsequent triplet codes are all altered, due to it being read in 3s

Question 17

What is a mutagenic agent?

Answer 17

a chemical, biological, or physical agent that causes changes to the DNA of a cell

Question 18

Name 4 mutagenic agents

Answer 18

-x-rays
-gamma rays
-benzene derivatives
-mustard gas

Question 19

What are the stages of meiosis?

Answer 19

prophase I
metaphase I
anaphase I
telophase I

prophase II
metaphase II
anaphase II
telophase II

Question 20

What happens in interphase?

Answer 20

DNA is replicated, the cell grows, and organelles are synthesised

Question 21

What causes variation in a species?

Answer 21

crossing over
independent segregation

Question 22

What is the chiasma?

Answer 22

the point of crossing over

Question 23

When does crossing over happen?

Answer 23

only in prophase I

Question 24

How does independent segregation happen?

Answer 24

homologous pairs attach to spindle fibres opposite each other in a random order, and the maternal and paternal chromosomes are not always on opposite sides. it only happens during metaphase I.

Question 25

How does independent segregation lead to variation?

Answer 25

the daughter cells will contain different, random assortments of the randomly separated chromosomes, so the gametes aren’t genetically identical

Question 26

How do you calculate how many variations there could be in meiosis due to independent segregation?

Answer 26

2^n –> where n equals the number of pairs

example- 2 pairs - 2 ^2 = 4 variations

Question 27

What is the point of meiosis I?

Answer 27

to separate the homologous pairs

Question 28

What is the point of meiosis II?

Answer 28

to separate the chromatids of the chromosomes

Question 29

What happens in prophase I?

Answer 29

chromosomes condense and shorten, and homologous chromosomes pair to form a bivalent
CROSSING OVER CAN HAPPEN HERE

Question 30

Compare meiosis to mitosis

Answer 30

meiosis-
-2 cell divisions
-4 daughter cells produced
-not genetically identical daughter cells
-gametes created
-crossing over can occur

mitosis-
-1 cell division
-2 daughter cells produced
-genetically identical daughter cells
-sematic cells created
-crossing over cannot occur

Question 31

When presented with a life cycle question, what is happening when it goes from 2n –> n?

Answer 31

meiosis, it is going from diploid to haploid

Question 32

When presented with a life cycle question, what is happening when it goes from n–> 2n?

Answer 32

fertilization, it is going from haploid to diploid

Question 33

How do you calculate the number of possible chromosome combinations produced from the fertilization of two gametes?

Answer 33

(2n)^2

where n equals the haploid number/ how many pairs there are

you must square it as you are joining gametes together

Question 34

What is non-disjunction?

Answer 34

when chromosomes fail to separate correctly during meiosis

Question 35

What is it called when you have extra whole sets of chromosomes?

Answer 35

polyploidy

Question 36

What happens when an organism has odd numbers of chromosomes?

Answer 36

the organism tends to be infertile as you cannot evenly half the them to form gametes

Question 37

When can’t you form gametes?

Answer 37

if you can’t form homologous pairs

Question 38

When could non-disjunction happen?

Answer 38

in meiosis I during the splitting of the homologous pairs

or

in meiosis II during the splitting of the chromosomes into chromatids

Question 39

What increases the chance of non-disjunction?

Answer 39

older age