Meiosis and Mutations

Question 1

Mutation

Answer 1

An alteration to the DNA base sequence.
Arises spontaneously during DNA replication, if during production of gametes, will cause distinct differences between parents and offspring

Question 2

Base Deletion

Answer 2

Mutation where a nucleotide in a gene is removed.
Causes a frameshift mutation

Question 3

Base Substitution

Answer 3

Mutation where a nucleotide in a gene is replaced by another nucleotide containing a different base.
This can be a redundant change due to the degenerate nature of the genetic code and the new triplet may still code for the same amino acid

Question 4

Frameshift Mutation

Answer 4

The entire sequence of bases is altered due to base deletion causing the bases to move to the left and thus each triplet is altered. Results in a completely different amino acid sequence.

Question 5

Mutagenic Agents

Answer 5

Increases the rate of gene mutation
Examples: ionising radiation, certain chemicals

Question 6

Polyploidy Chromosome Mutation

Answer 6

When organisms have more than the usual two sets of chromosomes, occurs mostly in plants.

Can occur if chromosomes do not separate into two distinct sets during meiosis producing gametes that are diploid. When they fuse with either haploid or diploid gametes the offspring has more than two sets of chromosomes.

Question 7

Non-disjunction Chromosome Mutations

Answer 7

Individual homologous pairs of chromosome fail to separate resulting in the gametes having a one more or one less chromosomes.
Offspring has more or less chromosomes than the usual number. Results in disorders such as Down’s Syndrome.

Question 8

Meiosis

Answer 8

Formation of gametes, haploid daughter cells which are genetically identical
One diploid cell to 4 haploid cells
Two cell divisions

Question 9

Meiosis I

Answer 9

Homologous chromosomes line up and their chromatids wrap around each other to form tetrads.
Homologous pairs separate (not individual chromosomes)
Independent segregation
Crossing over
Rest is same as mitosis

Question 10

Homologous Chromosomes

Answer 10

Chromosomes with the same position of gene on Chromosome (gene loci)
Combined pairs of homologous chromosomes are known as a bivalents

Question 11

Independent Segregation

Answer 11

Chromosomes line up alongside their homologous pair (one is maternal, one is paternal in Meiosis I, one of each pair goes to each daughter cell, which one goes to which is completely random. This introduces variation.

Question 12

Crossing Over

Answer 12

Sections of the chromosomes of the homologous pairs are exchanged, this happens in the chiasmata

Question 13

Meiosis II

Answer 13

Same as mitosis but no DNA replication, so daughter cells are haploid