Unit 5
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Whats is a gene mutation
a change in the base sequence of DNA
When do gene mutations occur
during DNA replication
What types of gene mutation are there
a base could be deleted, inserted or substituted with a different base
What is a substitution mutation also known as
a point mutation because the substitution happens at a single point on the DNA
What does it mean that genetic code is degenerate
more than one triplet codes for the same amino acid
Do all substitution mutations alter the protein being coded
no as the genetic code is degenerate so the same amino acid can be coded for with the mutated triplet
What level of protein structure will be affected if a mutation does have an affect
it affects the primary structure as the sequence of amino acids are altered
What does chromosome non-disjunction mean
either two chromosomes or two sister chromatids do not split from each other during meiosis
What is a mutagenic agent
anything that increases the rate of gene mutation above the normal level
Examples of mutagenic agents
radiation (UV) , heavy metals (lead) and some chemicals
What is a chromosome mutation
a change in the number of chromosomes that should be present in a cell nucleus
When do chromosome mutations occur
during meiosis
Examples of chromosome non-distinction
down syndrome, edwards syndrome, patai syndrome
What does the term diploid mean
a cell that contains two complete sets of chromosomes from each parent it is also called 2n
What does haploid mean
a cell that contains two complete sets of chromosomes, from one parent. also called n
What does n refer to in the context of haploid and diploid cells
n is the number of pairs of homologous chromosomes
What types of cell are haploid
gametes are always haploid so when they are fertilized they become diploid
Describe how daughter cells arise from meiosis
genetically different from each other are haploid cells
When is it important that meiosis is able to generate haploid cells
haploid gametes which can then be fertilized by another gamete maintains the chromosome number across generations
How many daughter cells arise from a cell undergoing meiosis
meiosis generates four haploid daughter cells from each diploid parent cell
How many times does the nucleus usually divide during meiosis
the nucleus usually divides twice to form four haploid daughter cells
What processes cause the haploid gametes to be genetically different
crossing over and independent segregation causes daughter cells to be genetically different
How does independent segregation cause genetic variation
it recombines maternal and paternal chromosomes when they align at the metaphase plate
What is a population
the number of the same species in a particular habitat