Cellular and Molecular Genetics Flashcards
what are 3 components of mendelian genetics?
- selection and transmission of genes
- dominance and gene expression
- genotypic basis of phenotypic outcomes
what are 4 components of molecular and cellular genetics?
- gene structure
- DNA as a blueprint
- DNA replication and error correction
- the cell cycle and genetic recombination
what is a gene?
- a region of DNA that controls a discrete hereditary characteristic, usually corresponding to a single protein or RNA.
- this encompasses the entire functional unit, including coding DNA sequences, noncoding regulatory regions, and introns
DNA is organized into ___
chromosomes
the genome is constructed of ___ chromosomes.
46
44 autosomes (22 pairs) and 2 sex chromosomes (1 pair)
DNA to RNA describes what?
transcription
RNA to protein describes what?
translation
DNA is wrapped around ___ to form nucleosomes
histones
eukaryotic DNA exists in long ___ strands
linear
DNA in nucleosome form is called ___
chromatin
draw out the cell cycle
- check points at the end of G1 and G2
what is LINE?
- long interspersed nuclear elements
- thought to be involved in gene silencing and regulation
what is SINE?
- short interspersed nuclear elements
- thought to be involved in gene silencing and regulation
during what phase is DNA replicated?
synthesis (S) phase
in the S phase, replication initiates at ___ origins, both DNA strands are ___, and DNA replication is ___
- replication
- replication bubbles are formed
- replication occurs in both directions
- templates
- semiconservative
in the S phase, DNA replication is semiconservative. what does that mean?
each of the two strands from the original “parent” DNA double helix serve as templates for a new strand
DNA is synthesized at ____
replications forks
in eukaryotic replication fork synthesis, what makes up the primosome?
DNA helicase and DNA primase
what holds together two chromatids to make a chromosome?
the centromere
what does DNA polymerase do?
polymerizes new DNA strands
what does topoisomerase do?
places nicks in the DNA to relax coils
what does DNA primase do?
creates RNA primers on the lagging strand
DNA polymerase replicates DNA, and chain growth occurs in what direction?
5’ to 3’
so, all of the base pairs are added to the 3’ end
what are the functions of polymerase alpha, beta, gamma, delta, and epsilon?
- alpha - RNA and/or DNA primers
- beta - base-excision repair
- gamma - mitochondrial DNA replication and repair
- delta - lagging-strand synthesis, DNA repair
- epsilon - leading-strand synthesis
what are 4 common DNA damages?
- mismatch
- deamination
- depurination
- double strand break
eukaryotic cells divide by ___ and ___
mitosis and meiosis (in that order)
draw out the mitosis phase
draw out the meiosis phase
the completion of interphase leads to ___
mitosis
what 3 things happen during interphase?
- the cell increases in size
- DNA of the chromosomes is replicated
- the centrosome is duplicated
what happens in the G1, S, and G2 phases of the cell cycle?
- G1 - protein synthesis, checkpoint
- S - DNA replication
- G2 - protein synthesis, checkpoint
what occurs in the prophase step of mitosis?
- chromosomes condense
- mitotic spindle assembles
what occurs in the prometaphase step of mitosis?
- nuclear envelope breaks down
- chromosomes attach to spindle via kinetocore, and undergo movement
what occurs during the metaphase step of mitosis?
- chromosomes align along the equator of the spindle between the poles
- kinetocore microtubules attach sister chromatids to opposite poles of the spindle
what occurs during the anaphase step of mitosis?
- sister chromatids separate to form two daughter chromosomes which move toward opposite poles
- kinetochore microtubules get shorter; spindle poles move apart
- chromosome separation
what occurs during the telophase step of mitosis?
- daughter chromosomes arrive at spindle poles and decondense
- nuclear envelope reassembles around individual chromosomes
- cytoplasm division begins and contractile ring starts to form
what occurs during the cytokinesis step of mitosis?
- cytoplasm is divided in two by the contractile ring
- actin and myosin filaments
- contractile ring pinches the cell in two, creating two new daughter cells
meiosis forms ___ gametes
haploid (1n)
what are 4 characteristics of meiosis?
- additional round of division
- genetic reassortment
- bivalents form during meiosis I
- genetic recombination occurs within bivalents in meiosis I
chromosome assortment increases ___
genetic diversity
general recombination exchanges ___ and ___ genetic content
maternal and paternal
recombination is directed by ___
recombinases
diploid starting cell: two different chromosome assortment patterns
meiosis I yields how many diploid cells?
meiosis II yields how many haploid cells?
what does this describe?
- 4
- 8
- independent assortment
describe recombination
- increases genetic diversity
- maternal and paternal chromosomes cross over and swap genetic information
- they then undergo independent assortment
chromosome assortment increases genetic diversity in what two ways?
independent assortment and recombination
general recombination occurs in bivalent chromosomes. what does this mean?
- pairing of duplicated homologous chromosomes forms a bivalent
- two kinetocores sit next to each other/ line up on the spindle
- recombination occurs
- genetic material is swapped
transposable elements create ___
site-specific recombination
what are the 3 classes of transposable elements?
- DNA-only transposons
- retroviral-like retrotransposons
- nonretroviral retrotransposons
age and genetic lineage can be traced by what?
identifying and locating transposons
what is the general function of retroviral-like retrotransposons and nonretroviral retrotransposons?
- produce RNA transcript, which is then put back into the genome as a DNA transcript
- undergoes an RNA intermediate
what is the cut-and-paste process of transposon insertion?
transposon is physically removed from DNA
what is the viral insertion process of transposon insertion?
viral DNA attacks particular region, integrates it into that portion of the DNA
what is the replication process of transposon insertion?
how are recombined chromosomes segregated?
- sister chromatids start to pull apart
- meiotic metaphase I
- arms of sister chromatids become unglued
- meiotic anaphase I
- brief interphase followed by m-phase with kinetochores functioning separately on each sister chromatid
- meiotic metaphase II
- sudden detachment of chromosomes (sister chromatids) at centromere
- meiotic anaphase II
genetic structure is altered
when are tetrads formed?
during metaphase I (meiosis I)
