Topic 4 Biology Flashcards
What is a mutagenic agent?
A factor that increases the rate of mutations.
What is disjunction?
In meiosis chromosomes not separated
Other than mutations what is one way genetic variation is increased within a species.
Random fusion of gametes produces new allele combinations.
Why are gametes genetically different?
Crossing over or independent segregation
Why does having too many chromosomes make something sterile.
Too many chromosomes so homologous chromosomes do not pair
So no meiosis
What is a gene mutation
A change in the base sequences of DNA which results in formation of a new allele
Explain how the chromosome number is halved during meiosis
The homologous chromosomes pair one of each pair goes to each daughter cell
What is the process of crossing over and how does it increase genetic diversity?
Homologous pairs of chromosomes associate
Chiasma forms
Equal lengths of chromatids exchanged
Producing new combinations of alleles.
Describe how mRNA is formed by transcription in eukaryotes
H bonds between DNA bases break
One DNA strand acts as template
RNA nucleotides align by complementary base pairing.
In RNA U pairs with A.
RNA polymerase joins adjacent RNA by phosphodiester bonds
Describe how a polypeptide is formed by translation of mRNA
mRNA attached to ribosomes
anticodons bind to complementary codons
tRNA brings specific AA which are then joined together by peptide bonds with use of ATP
TRNA released
Ribosome moves along mRNA to form polypetide
What is the fixed position occupied by a gene on a dna molecule
Locus/loci
What is an exon
Base sequence coding for a polypeptide
How is a phosphodiester bond formed between two nucleotides in dna
Condensation reaction between phosphate and deoxyribose catalysed by dna polymerase
Protein associated with dna in chromosome
Histone
