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67 Cards in this Set
- Front
- Back
What is RNA and DNA made of? |
phosphate group, 5 carbon sugar and nitrogenous base |
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what are the types of nitrogenous base and their pairs? |
pyrimidines: thymine and cytosine purine: adenine and guanine thymine pairs with adenine guanine pairs with cytosine |
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what is the shape of DNA |
anti- parallel, and a double stranded helix |
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what are the 3 levels of condensation of DNA |
1: packaging DNA into nucleosomes 2: supercoiling 3: attachment of fibres to a protein scaffold |
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explain the first level of condensation |
-starts as 2nm and goes to 11nm -146 nucleotide pairs wrap around an octamer of histones -wrapped around 8 histone proteins and anchored by 9th histone (H1) |
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whats a complete nulceosome in condenstation? |
8 histones, 146 base pairs and histone H1 |
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what can happen to linker DNA? |
linker DNA can be susceptible to digestion by endonuclease |
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what happens in the second level of condensation? |
-condenses to 11nm to 30nm -the nucleosomes wrap around each other |
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what happens in the third level of condensation? |
30nm fibre is attached at many positions to a protein scaffold |
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what are the two proteins used in the third level of condensation and what do they do? |
cohesin: proteins that hold the two arms together codensin: condenses the 30nm of chromatin within one sister chromosome |
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what are the three parts of the chromosomes? |
p arm: refers to the short arm q arm: refers to the long arm centromere: point of attachment of chromosomes microtubules in miotic spindle |
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what do telomeres do? |
protect the end of the chromosomes, prevent fusion and facilitate replications |
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where does mitosis occur? |
in all non-germ cells |
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what are the 5 phases of the cell cycle and what happens? |
G1: growth, cellular metabolism S: DNA replication G2: prep for mitosis M: mitosis interphase: time between successive mitosises |
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what is a sister chromatid? |
make up a chromosome and are identical |
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haploid vs diploid vs DNA content (in terms of n and c) |
haploid: 'n' and 'c' amounts of DNA, one chromosome diploid: 2'n' and 2'c', one unique chromosome from mom and dad |
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what are the 6 steps in mitosis |
interphase, prophase, metaphase, anaphase, telophase and cytokinesis |
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interphase: |
-chromosomes duplicate to produce sister chromatid -sister chromatid are homologs |
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prophase: |
-duplicated chromosomes condense -nulceolus disappears -nuclear membrane starts to breakdown |
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metaphase: |
chromosomes migrate to the middle |
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anaphase: |
sister chromatids pull apart and move to opposite poles of the cell -cohesin breaks down |
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telophase: |
chromsomes decondense and new nuclear membrane forms -new daughter cells are 2c and 2n |
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cytokinesis |
membrane forms between daughter cells |
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where does meiosis occur and what does it produce? |
-occurs in germ cells -results in 4 haploid genetically distinct cells |
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what are the steps in meiosis? |
meiosis I: prophase 1, metaphase 1, anaphase 1, telopahse 1 meiosis 2: prophase 2, metaphase 2, anaphase 2, telophase 2 |
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what are the steps in prophase 1: |
-leptonema: sister chromatids condense -zygonema: homologous coromosomes begin to pair -pachynema: crossing over occurs here -diplonema: homologous chromosomes seperate at the chiasmata |
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explain crossing over |
breakage of chromatids and the exchage of broken pieces between homologous chromosomes |
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what happens in metaphase 1 and 2? |
-1: paired chromosomes align in the middle -2: chromosomes align in the middle |
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what happens in anaphase 1 and 2? |
-1: homologous chromosomes disjoin andmove to opposite poles -2: sister chromatids disjoin and go to opposite poles |
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what happens in telophase 1 and 2? |
-1: new nuclei begin to form (n;2c) -2: haploid cells are seperated by cytoplasmic membranes (n;c) |
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whats the difference between a locus and an allele? |
locus: fixed position on a chromosome allele: alternate form of a gene (Aa) |
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what is a genotype? |
a genotype refers to the allelic combination |
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what is a phenotype? |
the physical appearance caused by the allelic combination |
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what is the difference between homozygous and and heterozygous? |
homozygous: both alleles and identical; either dominant or recessive heterozygous: two alleles are different |
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what are the three designations when doing crosses? |
P: parent generation F1: parents offspring F2: parents grand-offspring |
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what is the genotypic and phenotypic ratio for a monohybrid cross? |
1,2:1 and 3:1 |
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what is Mendel's principle of inheritance? |
in heterozygous, dominant allele masks the recessive |
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Mendel's principle of segregation? |
in a heterozygous, two alleles segregate from each other during formation of gametes |
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Mendel's principle of independent assortment? |
alleles on different pairs of chromosomes assort independently from one another |
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pseudoautosomal: |
found in the terminal region, genes that don't follow the X or Y linked pattern |
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What's the difference between heterozygous and hemizygous? |
heterozygous: recessive allele is masked by dominant allele (XX) hemizygous: recessive allele would manifest because there is nothing to mask it (XY) |
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what happens to the second X chromosomes in women? |
X- chromosome condenses into darkly staining matter called Barr Body |
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what is a spontaneous mutations? |
error during DNA synthesis when are isoforms of the bases occur |
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what are the alternate forms of the bases? |
keto-thymine: enol form amino-cytosine: imino form amino-adenine: imino form keto- guanine: enol form |
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what happens in the isoforms of the bases? |
adenine and cytosine bound and guanine and thymine bound |
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what are the hot spots for spontaneous mutations? |
simple repeats, symmetrical repeats and palindromes |
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what are the two types of chemical mutagens? |
-mutagenic only to replicating DNA(base analogues, acridine dye) -mutagenic to both replicating and non-replicating DNA |
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what can cause chemical mutations? |
UV rays can cause thymines to mutate into thymine dimers |
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what are transposable elements? |
virus puts segments into DNA which causes early stoppage |
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what are the type of single base (point) mutations? |
silent: no effect to resulting amino acid nonsense: results in early stop missense: changes one amino acid |
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what are the types of frameshift mutations? |
insertion: insertion of base pair, shifts coding to the right deletion: deletion of base pair, shifts coding to the left |
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expanding genes |
expanding genes show increased severity and severity earlier in life by generation |
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mutations that affect coding regions |
changes the protein to a non-functional form -premature truncation -changes protein folding -changes post- translational modification |
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mutations that affect non-coding regions |
prevent or reduce transcription or translation |
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what is incomplete dominance? |
one allele is partially or incompletely dominant over the other |
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what is codominance? |
heterozygotes express both phenotypes of both the homozygotes -blood type (AB) |
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what is the allelic series? |
a hierarchy displayed by the dominance of mutations within themselves |
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what is a test cross? |
if you want to find the genotype of something, cross is with a homozygous being |
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complementation test? |
cross two mutations together to see if a new mutation forms |
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what are the 3 stages in transcription? |
initiation, elongation and post-translational modifications |
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what happens in initiation (transcription)? |
RNA polymerase binds ta the DNA upstream of gene being copied (promoter) -rich in A's and T's |
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what happens in elongation (transcription)? |
-once bound to the promoter, the polymerase builds the mRNA single strand in 5prime to 3prime -only one DNA is copied, called the template strand -as polymerase passes, double helix reforms |
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what happens during post- translational modifications? |
-capping and tailing: 50- 250 adenines added to the 3prime, 5prime cap of 7 guanine to initiate translation -introns removed: introns are removed by spliceosomes as they don't code for amino acids |
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what are the 3 stages of translation? |
initiation, elongation and termination |
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what happens in initiation (translation)? |
-large and small ribosome subunits associate with mRNA -tRNA molecule containing amino acid Met joins to small ribosomal unit at the P site -complex binds to the 5prime cap of mRNA and large ribosomal subunit binds to complete ribosome |
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what happens in elongation (translation)? |
-tRNA is bound at the P site -next tRNA w/ anticodon and amino acid bind to A site -met is cleared and forms polypeptide bind with amino acid on A site tRNA -ribosomes move along the mRNA to the next codon and empty tRNA moves to E site and is released -tRNA move from A site to P site and new tRNA brings amino acid to A site |
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what happens in termination (translation)? |
-A site arrives at stop codon -polypeptide is released |