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Genetics is the branch of science concerned with
genes, heredity, & variation in living organisms
Where is genetic information stored?
Nucleus in DNA
How many strands are antiparallel?
two strands of DNA
How many strands are bound by hydrogen bonds?
two strands of DNA
G & C make how many hydrogen bonds… while T & A make _____ bonds
three, two
Purines consist of:
adenine and guanine
Pyrimidines consist of:
Cytosine, Uracil, Thymine
Each nucleotide consists of:
a sugar, phosphate, and a base
DNA & Histones are packed to form…
Nucleosomes
Nucleosomes are compacted in a helical shape called
Solenoid
Solenoid
assembled to form a loop and with a protein scaffold they form the Chromosome
True or false… Telocentric chromosomes only exist in humans
False
What are acrocentric chromosomes?
Chromosomes with the centromere located near one end, resulting in a long arm and a short arm.
Describe a submetacentric chromosome
A chromosome with the centromere located slightly off-center, creating two arms of unequal length.
What is a metacentric chromosome?
A chromosome with the centromere located in the middle, resulting in two arms of equal length.
Telomerase enzyme replaces the telomeres lost with…
DNA replication
Size of centromeres
0.3-5 Mb, for cell division
Haploid genotype
23 chromosomes, in gametes
Diploid genotype
46 chromosomes, somatic cells
What does the mitotic phase consist of?
mitosis and cytokinesis
Interphase is…
cell growth, copying of chromosomes in preparation for cell division including G1, S, and G2
G1 phase
the first phase of interphase where the cell grows and synthesizes proteins.
S phase
the phase of interphase where DNA is replicated, resulting in the duplication of chromosomes.
G2 phase
the second gap phase of interphase following DNA replication, where the cell continues to grow and prepares for mitosis.
Mitosis
Process of cell division (somatic)
In mitosis,
1 mother cell gives rise to 2 daughter cells
During mitosis each chromosome is separated
into the
two sister chromatids.
two sister chromatids replicate during…
the S phase of interphase.
Stages of Mitosis
Prophase, Metaphase, Anaphase, Telophase
What occurs during cytokinesis?
cell divides, 2 daughter cells form
What happens during telophase?
Mitotic spindle disappears, nuclear envelope begins to reform, cell division begins
Anaphase
mitotic spindle pulls sister chromatids to opposite poles
Cells are blocked in ______ to retrieve chromosomes
metaphase
G banding method
treatment with trypsin, and stained with dyes
Heterochromatin
dark, condensed DNA, not expressed
Euchromatin
light bands, less condensed, actively expressed
Autosomes
22 pairs
What does the CFTR location map gene 7q31.2 mean?
chromosome 7
q arm (long)
band 3
sub-band 1
sub-sub-band 2
Aneuploidy
loss or gain of 1 chromosome
Monosomy
missing one chromosome
Trisomy
one extra chromosome
Tetrasomy
not in humans
Polyploidy
gain of 1 complete haploid complement
Polyploidy can result in
Miscarriage
No cytokinesis
2 spermatozoa, fertilize 1 oocyte
Why don’t women suffer from having 2 X chromosomes?
Due to X inactivation, one is silent, the other is expressed (lyionization)
Inactivation is the condensation of: one X chromosome to form the…
Barr Body
Barr Body is:
an inactivated X chromosome that exists to complement the active form
Trisomy
21, 18, 13 (XXX, XXY, XYY)
Trisomy 13
Patau Syndrome
Trisomy 18
Edward’s Syndrome
Triple X syndrome
47, XXX
Klinefelter syndrome
47, XXY
Jacob Syndrome
47, XYY
S phase: DNA replication
Sister chromatids identical, replicated during synthesis
One chromatid is used as a template
New DNA molecules are made up of one of the ________ plus
a new half.
As a result, DNA replication is
called ______
original parental strands
semi-conservative
DNA Polymerase synthesizes DNA using a template and works in a ____________
5’ to 3’ direction
Each bubble on chromosome allows for:
replication for a leading strand and a lagging strand
Okazaki fragments are synthesized in the…
lagging strand
DNA polymerase requires ____ to function
primers
primers
short RNA sequences (~20 nu) from which the DNA
poly can start to amplify DNA
exonucleases
they can degrade the RNA primers they find ahead and replace them
with DNA, they cannot seal the nicks
Initiation
Proteins bind to DNA, open up double helix, and prepare DNA
Elongation
Proteins connect the correct sequence of nucleotides into a continuous strand of DNA
Termination
Proteins release the replication complex to cut the DNA to avoid
tension damage caused by overwinding to stabilize SS DNA
Helices
Separates 2 strands
Primase
Synthesizes RNA primers
Single strand binding proteins
Prevents reannealing of single strands
DNA ligase
Seals nicks in DNA
DNA polymerase
Synthesizes DNA, polymerases in eukaryotes also function as an exonuclease
Telomerase
enzymes that restore telomere length to avoid DNA loss (only in certain cells)
Topoisomerase
Prevents torsion/breaks
Pseudogenes
not expressed, 𝛹, resemble coding genes, produced by gene duplication/inactivating mutations
Tandem
they are clustered together and oriented in
the same direction
Microsatellites
2-4 bps 10-30 repeats
Rarely on coding genes, can cause disease
Minisatellites
telomeres, hypervariable minisatellite
Satellites
several hundreds bps clustered around centromeres
transposable element
a DNA sequence that can change its position within a genome
Transposons
create or reverse mutations and
alter the genome size, thus creating genetic
diversity
TE can make up to _____ of human genome
45%
How do TE work?
DNA Transposons, Retrotransposons
SINEs Short Interspersed Nuclear Elements
~300 bp in 1 millin copies (Alu)
10% of genome
Originated from transposons - have short sequences recognized by tranposases
All are retrotransposons
LINEs Long Interspersed Nuclear Elements
17% of human genome
Line-1 in 6000 bp in > 100,000 copies
Line 1 is a Retrotransposon
Coded for transposes enzyme
Alu elements can cause disease by…
insertion, homologous recombination
Mitochondria contain a
16.6 kb circular ad double-stranded genome
DNA directs the production of proteins
via an intermediate molecule of DNA
F, RNA
exons
coding regions
introns
non-coding regions that are
removed during the splicing process
Capping is the addition of a 5’ cap, which facilitates…
mRNA export and protects the molecule
200 adenines are added to the 5’ end to facilitate
export
3’ end, F
Translation takes place in the…
cytoplasm by ribosomes, made of rRNA and proteins
Ribosomes read mRNA and use tRNA to produce a string of amino acids by ___________ on the mRNA with nucleotides on the tRNA
pairing up nucleotides
3 nu on the tRNA make an ______
3 nu on the mRNA make a ________
Each tRNA also binds one of ______
anticodon, codon, 20 AAs
Gametogenesis
oogenesis and spermatogenesis
Crossing over
occurs when homologous chromosomes line
up during meiosis I.
Meiosis is arrested in _____ (diplotene) at birth
prophase I
With ovulation, meiosis continues and is arrested at _________
metaphase II
Non-disjunction
he failure of homologous chromosomes or sister
chromatids to separate properly during cell division
There is two globin chains on alpha 1 and alpha 2
T
The coding strand (DNA) - TTC
Find the Template:
mRNA (Codon):
Anticodon tRNA:
AAG, UUC, AAG
Synaptonemal complex
keeps homologous chromosomes together until pregnancy
