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BIOL 207 > FIRST MIDTERM > Flashcards

FIRST MIDTERM Flashcards

1
Q

Compare c value and n value contained in a cell.

A

C-value refers to the amount of DNA usually measured in base pairs.
N-value refers to the number of chromosomes found in the haploid cell

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2
Q

Differentiate haploid and diploid cells.

A

Haploid cells contain a single set of unpaired chromosomes, while diploid cells contain a homologous pair of every chromosomes.

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3
Q

What are bivalents?

A

Homologs pairing during Prophase I

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4
Q

What does crossing over mean?

A

Physical exchange of DNA b/w nonsister chromatids of homologs

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5
Q

What is a ter sequence?

A

Ter sequence refers to the termination sequences located opposite of the origin sequence

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6
Q

What is the function of the TUS protein?

A

TUS protein recognize and bind ter sequence and prevents further opening of the replication fork

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7
Q

What are ORCs?

A

ORCs are origin recognition complexes which bind origin of replication. They recruit DNA polymerase.

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8
Q

What does the PULSE-CHASE experiment involve?

A 
PULSE = exposure and incorporation of a labelled reagent
CHASE = removal of labelled reagent from medium
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9
Q

What are nucleosomes?

A

DNA wrapped around proteins called histones

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10
Q

What is the function of CAF1?

A
  • Delivers new histones to replicated DNA (need to double the amt of histones)
    • Recognizes PCNA (a processivity factor of DNA pool)
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11
Q

Differentiate between condensins and cohesins.

A

Condensins bundle chromatids while cohesins link sister chromatids together.

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12
Q

What are telomeres?

A

Telomeres are repeated sequences found at the end of linear chromosomes, they are non-coding DNA and do not have coding information.

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13
Q

What are telomerase?

A

Telomerase are enzymes that extends telomeres by adding short repeats to the 3’ end of the chromosome using a small RNA template

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14
Q

What are operons?

A

A set if coordinately controlled genes. In prokaryotes, they are gene clusters where several genes lie in tandem and are governed by the same promoter and the same inhibitory and stimulatory mechanisms

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15
Q

Differentiate exons and introns.

A

Exons are expressed or the coding region while introns are the intervening sequence or the noncoding region.

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16
Q

What are positive regulators and give an example.

A

Proteins that bind DNA and promote transcription.

MyoD in eukaryotes binds to DNA and turns on transcription. It recognizes specific sequence in minor groove.

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17
Q

What are negative regulators?

A

Negative regulators are proteins that bind DNA and prevent transcription.

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18
Q

How does Lac I work?

A

Lac I is a heterodimer that binds to DNA and represses lac operon expression by:

  • preventing RNA polymerase from associating with promoter
  • by preventing RNA polymerase from moving down the DNA
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19
Q

How are operons regulated in prokaryotes?

A

Operons are transcribed as a single mRNA with multiple coding regions. They are regulated at the OPERATOR where the cell can sense different environment cues to turn on or off the operon.

20
Q

What happens to the lac operon in the absence of lactose in prokaryotic cells?

A

In the absence of lactose, Lac I binds to the operator and the transcription is blocked.

21
Q

In the presence of lactose, what happens to Lac I?

A

Lactose is an allosteric inhibitor of Lac I. In its presence, Lac I loses its regular shape making it unable to bind to the DNA and inhibit lac expression. Therefore, Lac Z, Y and A are now expressed.

22
Q

What is the difference between genotype and phenotype?

A

Genotype is all of an organism’s genes/DNA, while phenotype is the expression/manifestation of genotype.

23
Q

What is the difference between cis-acting and trans-acting mutations?

A

Trans-acting mutations: can act on sites other than the DNA molecule on which the mutation is located. Generally, these are genes for products (Proteins or RNAs) that can influence the expression of other genes or interact with the products of other genes.
Cis-acting mutations: only affects sites located on the same DNA molecule as the mutations. They do not code for gene products but are sites that can influence nearby gene expression. (E.g. Mutations on the promoter)

24
Q

Explain the logic of arranging genes in an operon.

A

Operons are arranged so that one regulatory event can control the expression of several genes that are required normally in the same pathway. Operons are regulated by having an operator region that controls a set of genes upstream of the transcription start site.

25
Q

Why do eukaryotes do not organize genes like how prokaryotes organize theirs in an operon?

A

Multicellular organisms often have different requirements for different regions in their genes, therefore co-regulating would be a waste of energy. Eukaryotes have introns and more complicated gene structure that does not make them amenable to polycistronic messages.

26
Q

What is a genetic locus?

A

A sequence in the genome that gives rise to a testable phenotype

27
Q

What is the difference between homozygote and a heterozygote?

A 
Homozygote = organism with identical alleles at the gene of interest
Heterozygote = an organism with different alleles at a gene of interest
28
Q

What is a wild type allele?

A

Commonly accepted normal form in a genetic organism

29
Q

What does haplosufficient mean?

A

One copy of an allele is sufficient for full phenotype

30
Q

If mutant allele is RECESSIVE, the wild type allele is ____________.

A

Haplosufficient. This means one copy of wild type allele is sufficient to give wild type phenotype.

31
Q

If mutant allele is DOMINANT, wild type allele is ____________.

A

Haploinsufficient. This means that one copy of wild type allele is NOT sufficient to give wild type phenotype.

32
Q

What are Mendel’s conclusion about inheritance after his research?

A
  1. Existence of genes
    1. Genes are in pairs
    2. Dominance vs. Recessiveness
    3. Halving of gene pair in gametes
    4. Equal segregation
    5. Independent assortment
33
Q

What is a monohybrid cross?

A

A cross between two individuals identically heterozygous at one gene pair.

34
Q

What does true breeding mean?

A

A group of identical individual organism that always produce offspring of the same phenotype as the parents.

35
Q

What is a test cross?

A

A cross of individual organism of unknown genotype with a tester. This is done to a) determine the genotype of an unknown individual or b) test linkage.

36
Q

What is a tester?

A

A tester is an individual organism homozygous recessive for all alleles being tested.

37
Q

How does law of segregation tie in with our understanding of meiosis?

A

Alleles segregate in anaphase I (and it’s a 50/50 chance)

Each gamete gets one allele

38
Q

What does Mendel’s First Law state?

A

The two members of a gene pair segregate from each other into the gametes so half the gametes carry one member of the pair and the other half of the gametes carry the other member of the pair.

39
Q

What is a dihybrid cross?

A

A cross between two individuals identically heterozygous at two loci.

40
Q

Mendel’s Second Law states that:

A

Unlinked or distantly linked segregating gene pairs assort independently at meiosis.

41
Q

What is a reciprocal cross?

A

A reciprocal cross is when you swap sexes of the parentals to determine if a gene is on an X-chromosome. This performed when you want to determine of the gene is sex-linked.

42
Q

What are auxotrophs?

A

Organisms that cannot grow on minimal media and they can only grow when minimal media (MM) is supplemented with a specific substance. Also called “metabolic mutants”.

43
Q

What are prototrophs?

A

Prototrophs are organism that will grow on minimal media.

44
Q

What does a minimal media (MM) contain?

A

Lab growth media containing a sugar, inorganic salts + water.

45
Q

What does Complementation mean?

A

The production of a wild type phenotype when two different recessive mutations are combined in a diploid or heterokaryon.

46
Q

Explain the logic behind the complementation test.

A

In crossing two mutant lines, if heterozygote shows mutant phenotype, then the 2 mutations are within the same gene type (i.e. If they do not complement, they’re allelic). If heterozygote shows wild type phenotype, then 2 mutations are in a different gene (i.e. if they complement they are NOT allelic).

BIOL 207 (1 decks)

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