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40 Cards in this Set
- Front
- Back
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What does it mean to say that human beings are diploid?
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They have two copies of the genome in each cell.
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How many base pairs is the human genome?
What is the average length of a chromosome? |
3 billion base pairs. And all diploid cells have two copies (6 billion).
125 million base pairs long |
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How many mature eggs develop from each diploid oocyte?
How many sperm develop from one diploid spermatocyte? |
Only ONE egg develops. 3 genomes worth of genetic material is lost in the polar bodies.
FOUR sperm come from one spermatocyte. |
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What is non-disjuction?
What is an incorrect number of chromosomes called? |
Failure of chromasomes to segregate properly during mitosis, meiosis 1 or meiosis 2.
Anueploidy = wrong # chromosomes. |
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What inhertitance pattern does hereditary nonpolyposis colorectal cancer follow?
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HNPCC is autosomal dominant
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When looking at a pedigree- what indicated autosomal dominant?
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1. When both males and females have the disease.
2. When about 50% of the off-spring with an affected parent are also affected. CANNOT SKIP A GENERATION - if the next generation doesn't get it...it stops. |
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What inhertitance pattern does Cystic Fibrosis follow?
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Cystic Fibrosis is autosomal recessive.
Only occurs if both parents are carriers/affected. CAN SKIP GENERATIONS. |
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What inhertitance pattern does Ehlers-Danlos syndrome follow?
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BOTH autosomal recessive (mutation in procollagen aminopeptidase) cases
and autosomal dominant cases (mutation in alpha2). |
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What inhertitance pattern does Lesch-Nyhan syndrome follow?
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Lesch-Nyhan syndrome follows X-linked recessive pattern.
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Explain what it means for a female to be mosaic for X-linked recessive traits.
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Only one X gene is activated in each cell - and it can be a different homolog for any given cell. So in females, every cell can express only one allele of X-linked locus--> in the body as a whole, both alleles are expressed equally.
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What is this?
How do you know? Where is it found? |
Ribose
There is a 2' OH group. Found in RNA. |
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What is this?
How do you know? Where is it found? |
deoxyribose
There is do 2' OH group. Found in DNA |
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What is this?
How do you know? |
Adenine
it has TWO rings. It has an NH2 group but NO carboxyl group. |
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What is this?
How do you know? |
Guanine
It has TWO rings. One NH2 group and one carboxyl group. (More exciting groups than adenine) |
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What is this?
How do you know? |
Cytosine
It has ONE ring. One NH2 group and one carboxyl group. It reminds me of a single ring-ed guanine. (and G and C go together...making 3 H bonds = most stable). |
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What is this?
How do you know? |
Thymine
it has ONE ring. TWO carboxyl groups and a super sweet CH3 group. (only one like that). |
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What is this?
How do you know? |
Uracil
It is ONE ring. Has TWO carboxyl groups (just like Thymine) but that's it. NO methyl group. |
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Which base pairing is the most stable? Why?
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G-C is most stable because it makes 3 H-bonds.
A-T only makes 2 H-bonds. |
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What stabilizing factors keep DNA strands together?
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1. hydrophobic stacking interactions of the base pairs.
2. H-bonds between bases. |
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What is the difference between reannealing and hybridization?
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reanneal means when two originally paired strands go back together as they were.
Hybridization means two previously unpaired strands go together. |
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What happens in G1 phase of the cell cycle?
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The cells have just gone through Mitosis and are taking a break before going through replication. MOST CELLS ARE IN G1 phase!
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What is happening during S phase of the cell cycle?
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cells have just left G1 and the DNA is replicating itself...producing sister chromatids. G2 follows S phase.
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What happens during the G2 phase of the cell cycle?
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During G2...the sister chromatids that were just made in the S phase are hanging out..getting ready to say goodbye.
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What does DNA polymerase need to function?
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DNAP needs a template strand AND A PRIMER (which can be DNA or RNA
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Why doesn't the reverse rxn occur with DNAP?
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When DNAP works - it pops off a PPi group. Then pyrophosphatase comes around and cleaves that...giving off energy needed to fuel polymerization.
KEEPING [PPi] LOW keeps this from reversing. |
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How is the lagging strand replication different from the leading strand?
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The lagging strand needs constant influx of new RNA primers bc it still needs to be made 5' to 3'.
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What makes the RNA primers used to replicate the lagging strand?
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DNA primase makes short RNA primers that are extended by DNAP making okazaki fragments. These are later replaced by DNA and joined together by DNA ligase.
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What repairs DNA in replication when DNA Polymerase adds a mismatched base?
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3'-5' Exonuclease activity of DNA polymerase hydrolyzes and releases a dNMP. The DNAP 5'-3' activity will add the right one.
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What is a replication bubble?
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It would take a week for DNAP to replicate an entire chromasome...so more than one DNAP is going at a time making "bubbles" that merge.
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What is the every end of a chromosome called?
What prevents a lagging strand from becoming shorter each rep. cycle? |
A telomere.
Telomerase - it adds many copies of a simple sequence of nucleotides to the 3' end of a chromosome. Telomerase is a REVERSE TRANSCRIPTASE |
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What is a topoisomerase?
What if a cell had no topoisomerase? |
It prevents supercoiling in DNA strands.
Without this the DNA strand would supercoil and replication would halt = cell death. |
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What is cross-over?
When does it occur? Is it more common in maternal or paternal homologs? |
meiotic recombination.
Occurs between homologous chromatids during meiosis I. More common in maternal meiosis. |
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When are two loci linked?
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When they are the distance between two loci are 1cM apart.
Loci more than 1/3 of the length of the chromosome apart will not be linked. |
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What is a haplotype?
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A collection of alleles found together on a single chromatid.
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How does unequal recombination cause alpha-Thalassemia?
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Crossover between mispaired genes delete one of the alpha-globin genes from one chromatid and adds one to another. A child who inherits a single alpha-globin will make half as much globin as normal = mild anemia.
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What are the two most commonly dispersed repeated DNA sequences in the human genome?
How did this happen? |
Alu family and the LINE family
these both result from intrachromatid homologous recombination. |
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What is a transposon?
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active transposable elements - they can generate copies of themselves that insert into the genome. THis is how Alu and LINE became so numerous in thee genome.
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What is the purpose of VDJ-joining?
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This is somatic rearrangement that B-cells do to make our immune system more specific.
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What are TRECs?
What does absence of these in blood indicate in newborns? |
These are small circular DNAs corresponding to deleted regions of T-cell receptor genes.
Absence of these used to detect SCID (deaminase deficiency) in newborns. |
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What is a copy number variation in DNA?
What detects these best? |
Every genome has changes in copy number of certain genes from problems with recombination.
aCGH (array comparative genome hybridization) detects this. |
