Human Genetics 3 Flashcards
steps of dna replication
- helicase unwinds
- single strand binding proteins keep unwound
- primase adds short RNA primer
- leading strand synthesised by polymerase III 5’ >3’ (reading off 3-5)
explain lagging /leading strand
- Extension of the strand can only happen in 5’-3’ direction
• Only one strand can get extended continuously= leading strand
- Other strand created discontinuously = lagging strand
- Gets replicated by addition of short Okazaki fragments
explain polymerase 1 and ligase do
lagging strand
- 1. Enzyme DNA polymerase I replaces RNA primers with DNA
• Enzyme DNA ligase closes the polypeptide stands
What are DNA polymerases proof reading roles
- Excision of incorrectly incorporated nucleotides by 3’ > 5’ exonuclease activity
- mistake gets corrected before more of the strand with the error is created
what are the 3 levels of mutation
gene
chromsome
genome
3 types of gene mutation
- Base subs
- Base insertion or deletion
- Copy number variation
3 types of chromosomes mutation
- Inversion
- Translocation
- Deletion
type of genome level mutation
- Change in number of chromosomes
what the universal start codon bases
AUG
What are base subsitutions
point mutations= single nucleotide polymorphisms
• Replacement of one nucleotide in DNA by another (T -> C)
three types of base substitutions
synonymous(silent)= same AA
missense (changed AA)
Nonsesnse = STOP codon
what are base insertions/deletions also known as
frameshift mutation
what can copy number variation gene mutation effects in cell
amount of protein made
what translocation
• Fragment of a chromosome is moved from one chromosome to another
what are two options of division of stem cells
self renewal
differentiaition
what are the two signals that cause differentiation of stem cells > diff tissues
- Internal signals: changes in transcription or expression of genes expression regulates cell differentiation
- External signals: chemicals secreted by other cells, physical contact with neighbouring cells, molecules in the microenvironment of the cell
prevalence vs incidence
Prevalence: number of people alive with a prior diagnosis of cancer at a given time
Incidence: number of new cancers diagnosed within a given period of time
3 causes of cancer
genetics
oncoviruses
environment
two types of reproduction
asexual and sexual
advantages of asexual reproduction
Speed, no gamete formation necessary – very quick
Advantage for small populations e.g. in secluded areas
Not very complex, requires less energy compared to sexual reproduction
Advantage in stable environment
disadvantages for asexual reproduction
Offspring is clone of parent -> little genetic diversity
Environment usually not stable long term -> want to have
diversity to be able to adapt to different environments
Often struggle for existence as well as overcrowding
advantages of sexual reproduction
Introducing genetic diversity
-> allows for adaptation to a changing
environment
disadvantages of sexual reproduction
Cost intensive – a lot of energy
Only 50% of the genome contribute to
the offspring
Fewer offspring
Prep for meisosis= what does DNA replication do
2n (one maternal one paternal)
> two maternal two paternal (connected at centromere)
what two processes results in variation in sexual reproduction
crossing over
independent assortment
what are the division names of meiosis 1 and 2 and main divisional occurrences
Meiosis I: Reductional Division (homologous chromosomes seperate)
Meiosis II: Equational Division (sister chromatids seperate)
explain stages of meiosis I
P1: condense + form chromosomes, crossing over occurs
M1: align at equator
A1: homologous chrome opposite poles by spindles
T1: reform nucleus
at the end of Meiosis 1, are they haploid or diploid
haploid= but have chromo still duplicated
what is interkinesis
period b/w 1st 2nd meiosis
stages of meiosis II
same as Meiosis I but at anaphase sister chromosomes split
at the end of Meiosis II, are they haploid or diploid
4 haploid cells (n, 23)
