Genetics Flashcards
Whenever there’s a “never” on an exam…
It’s wrong
Medel’s 2 Laws:
Segregation - gamete will have one allele or the other
Independent Assortment - alleles are mixed up
2 arms of a chromosome:
p - short arm
q - long arm
How many chromosomes in a human?
46
23 pairs
(22 pairs plus XX or XY)
What are the 3 positions of the Centromere:
Metacentric - in middle
Submetacentric - off center with different arm lengths
Acrocentric - centromere near top
What is at the end of chromosomes?
Telomeres
What are 2 arms of a replicated chromosome held together at a centromere?
Sister chromatids
3 parts of Interphase:
G1 -
S - DNA replication (synth)
G2
6 phases mitosis:
Interphase (G1, S, G2)
Prophase (chromosomes condense)
Prometaphase (nuclear mem. disappears)
Metaphase
Anaphase
Telophase (cytokinesis)
At what point in Meiosis is there separation of centromeres?
Meiosis II
Describe Meiosis I:
Reduction Division
Homologues separate
46 > 23 / (2n > 1n) / diploid > haploid
Describe Meiosis II:
Sister chromatids separate
Where does Crossover occur in Meiosis?
Prophase I
In recombination, homologous chromosomes line up and crossover, producing ______ and _____ gametes
2 parental
2 recombinant
The number of cross-over events is related to the _____ of the chromosome arm.
Length
T/F
Decreased cross-overs are associated with increased risk of nondisjunction
True
What are the products of Oogenesis?
1 oocyte
2 polar bodies
*1st polar body doesn’t divide again
4 aspects of Male Meiosis:
Puberty onset
60-65 days
4 spermatids
100-200 million/ejaculate
4 aspects of Female Meiosis:
3rd month embryo onset
10-50 year duration
1 ovum, 2 polar bodies
1 ovum per menstrual cycle
Prophase I of Meiosis (M1) 5 stages:
Leptotene - condensation
Zygotene - homologs pair
Pachytene - crossing over
Diplotene - homologs separate incompletely (still chiasma)
Diakinesis - homologs completely separate
Nondisjuction at M1 (prophase I) will result in _____ and _____ gametes.
*Homologues don’t separate
2 Disomic
2 Nullisomic
*heterodisomy
The Disomic Gametes of M1 nondisjuction are?
Heterodisomy
Nondisjuction at MII will result in _____ and ______ gametes.
*homologues separate, sister chromatids don’t
2 Disomic
2 Nullisomic
*isodisomy
The Disomic Gametes of MII nondisjunction are?
Isodisomy
After meiosis II, the daughter cells contain…
23 chromosomes, 23 chromatids
Kb =
Mb =
cM =
1% recombination =
1000 bp
1 million bp (1000 Kb)
1 Mb
1 cM
How do we count chromosomes?
By the number of centromeres present
At the beginning of Meiosis I, how many Chromosomes does the cell contain?
46 chromosomes
At the beginning of M1, how many Chromatids does the cell contain?
92 chromatids
At the end of M1, how many Chromosomes does the cell contain?
23 chromosomes
At the end of M1, how many Chromatids does the cell contain?
46 chromatids
At the end of Meiosis II, how many chromosomes does the cell contain?
23 chromosomes
At the end of MII, how many Chromatids does the cell contain?
23 chromatids
Immediately after fertilization, how many chromosomes does the zygote contain?
46 chromosomes
Immediately after fertilization, how many Chromatids does the zygote contain?
46 chromatids
The zygote prepares to divide. Immediately before the first mitotic division, the cell contains how many Chromosomes?
46 chromosomes
The zygote prepares to divide. Immediately before the first mitotic division, the cell contains how many Chromatids?
92 chromatids
In a 2 cell embryo, how many Chromosomes are in each cell?
*immediately after mitotic division
46 chromosomes
In a 2 cell embryo, how many Chromatids are in each cell?
*immediately after mitotic division
46 chromatids
How many chromosomes do humans have?
46 chromosomes
If short arms and large arms are about the same length and the centromere is in the middle, the chromosome is said to be…
Metacentric
If the centromere is off center, the chromosome is…
Submetacentric
If the centromere is extremely off center, the chromosome is…
Acrocentric
P is the ____ arm
Q is the ____ arm
petite - short
long
Telomeres are at the _____, centromeres are in the ____.
end
middle
What is the Growth stage between mitosis and replication (preparing to replicate)?
G1
DNA replication phase:
Interval between synthesis and mitosis (repair):
S
G2
2 aspects of Prophase:
Chromosomes condense
Mitotic spindle/centrosomes begin to form
What happens in Prometaphase?
Nuclear membrane disappears
3 aspects of Metaphase:
Chromosomes fully condense
Chromosomes line up on meta plate
Spindle fibers begin to contract
2 aspects of Anaphase:
Centromeres divide into 2
Spindle fibers pull chromatids apart by centromere
4 aspects of Telophase:
Cytokinesis
2 nuclear membranes
Spindle fibers disappear
Chromosomes revert to uncondensed form
Time in each:
G1
S
G2
10-12 hrs
6-8 hrs
2-4 hrs
At the beginning of M1, a human cell contains ______ chromosomes and ______ chromatids.
46
92
In M2, 2 cells have _____ chromatids each containing _______ chromosomes
46 chromatids
23 chromosomes
At the end of M2, 4 cells have ___ chromosomes and __ chromatids.
23
23
Sperm =
Egg =
Zygote =
23 chromosomes (23 chromatids)
23 chromosomes (23 chromatids)
46 chromosomes (46 chromatids)
Male gametogenesis produces:
Female gametogenesis produces:
w/ w/out fertilization
4 sperm cells
1 Egg, 2 Polar bodies After fertilization
1 Egg, 1 Polar body without fertilization
What is the average size of a gene?
Hoe many genes in the human genome?
14,000 bp (14 kb)
22,000 genes
cM = ____ Mb = _____ kb = ______ bp DNA
1
1000
1,000,000
1 cM = ___% recombination
1%
*1 million bp
What is at the beginning of a gene?
What sequences were previously known as junk DNA?
What are the coding sequences?
5’ un-translated region
Introns
Exons
DNA > DNA
DNA > RNA
RNA > Protein > Translation
Replication
Transcription
Translation
How many codons total?
64
How many AA’s have only 1 codon?
What are they?
2
Trp - Tryptophan - UGG
Met - Methionine - AUG - start codon
How many stop codons?
What are they?
3
UAA, UAG, UGA
Is the code the same for nucleic and mitochondrial DNA?
No.
Mitochondrial DNA uses Non-Universal codon
Single generation, clustered form of inheritance:
If sister expresses an Autosomal Recessive disorder, the chances of being a carrier are:
Autosomal recessive
2/3
Every generation affected, evenly distributed trait pattern:
Autosomal dominant
*Vertical Transmission
What inheritance pattern looks like vertical recessive because it skips generations?
Non-penetrance of Dominant trait
Vertical transmission appearing out of nowhere?
New mutation - Dominant
A genetic disease that can be mild in one pt and severe in another may be exhibiting what?
Variable expressivity
Transmission that is expressed in males only?
X-linked
***female carriers
5 ways a female can have an X-linked disorder:
recessive
consanguinity
Assortative mating
Isodisomy
Lionization
Turner’s syndrome
If mother passes trait on to all, and sons don’t pass but daughters do…
Mitochondrial
What are the 2 best examples of Imprinting in humans?
Prader-Willi
Angelman
What is the most common mechanism that causes PWS?
Minority?
Deletion of father’s chromo 15 (70%)
Maternal uniparental disomy (25%)
What is the most common mechanism for Angelman Syndrome?
Deletion on mothers chromo 15 (70%)
______ is the most efficient way to test PWS and AS.
Methylation Analysis
Uniparental Disomy has implications for what 2 types of disorders.
Recessive
Imprinted
6 Components of PCR:
DNA template
Primers
dNTP’s
polymerase
Buffer
Mg
What 3 steps make up a cycle of PCR?
Denaturation
Annealing
Extension
