MGD7+8 Flashcards
Where does the energy come from for DNA replication?
The hydrolysis of pyrophosphate
What are the steps of initiation for DNA replication?
recognition of the origin of replication
recruitment of DNA polymerase
‘kick-start’ by primase
small amount of RNA made that can be extended and then RNA bit is removed
What makes up the lagging strand?
Okazaki fragments
On chromosomes, which arm is usually shorter?
The p arm
What type of chromosome do humans not have?
Telocentric
How long does it take a human cell to replicate all of its DNA?
8 hours
What happens in telophase of mitosis?
nuclear membrane reforms, chromosomes decondense and spindle fibres disappear
What happens in prophase I of meiosis?
homologous chromosomes find each other to form bivalents
crossing over occurs at chiasmata
What happens in metaphase I of meiosis?
homologous pairs line up on equator (metaphase plate)
random assortment of chromosomes
What happens in anaphase I of meiosis?
chromosomes are pulled to opposite ends of the cell
What is the difference between meiosis I and meiosis II?
in anaphase II the sister chromatids are split up and pulled to opposite ends of the cell instead of the chromosomes
How long does spermatogenesis take?
48 days
What is the sequence for spermatogenesis?
spermatogonium (2n) -> primary spermatocyte (2n) ->
spermatids (n) -> mature sperm (n)
What is the sequence for oogenesis?
Oogonium (2n) -> primary oocyte (2n) -> 1 egg (n) + 3 polar bodies
What does hemizygous mean?
can only occur in men, it means they only have 1 allele of a gene as it is on the X chromosome
What are the most common patterns on inheritance and give an example for each?
autosomal recessive eg. cystic fibrosis
autosomal dominant eg. Huntington’s disease
X linked recessive eg. Haemophilia A
What does it mean if alleles are codominant?
They both contribute to the phenotype
Give an example of codominance
Human blood types
Give an example of complementation
Albinism
What is the basis of complementation?
The basis is that more than one gene can be involved in producing the phenotype.
Sometimes you have to have the mutant allele in both to have the disease.
What are linked genes?
Genes on the same chromosome
Do linked genes show independent assortment?
No
They are on the same chromosome so are most likely carried together.
If 2 genes are further apart on a chromosome how does this affect the recombination frequency?
The recombination frequency is likely to be higher the further apart the genes are on the chromosome.
Which enzyme catalyses DNA replication?
DNA polymerase
