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Cell Biology Test 3 > Test 4 > Flashcards

Test 4 Flashcards

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1
Q

What was Darwin’s Idea of Genetics?

A

Did NOT accept the idea of blending
- Some forms of traits help individuals survive and reproduce, those traits would appear more frequently in a population over generations

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2
Q

Mendel’s Work and Results

A
  • Cross-fertilized pea plants and observed traits were passed from plant to plant over many generations
  • Transferred pollen among individuals with different traits
  • Hereditary info is passed from one generation to the next
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3
Q

Homozygous

A

An individual that had IDENTICAL alleles of a gene
ex.) organisms that breed true for a particular trait AA

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4
Q

Genotype

A

Particular set of alleles that an individual carries
ex.) B= Brown eyes; b= blue eyes; BB, Bb, bb=genotype

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5
Q

What is considered a major source of variation?

A

Alleles

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6
Q

How are new alleles produced?

A

As a result of MUTATION; may cause a trait to change

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7
Q

Phenotype

A

An individual’s OBSERVABLE traits
ex.) flower color

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8
Q

What is a mutated gene considered?

A

An allele

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9
Q

Hybrids

A

An offspring that is produced in a result of crossing 2 individuals that bred true (BB, bb) for different forms of a trait

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10
Q

Heterozygous

A

Carry different alleles of a gene (Bb)
ex.) hybrids

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11
Q

Dominant

A

When the allele masks/overcomes that of recessive alleles
ex.) B

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12
Q

Recessive

A

Alleles that are overcome by dominant alleles
ex.) b

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13
Q

Mendel’s Law of Segregation

A

Evidence of a dominant relationship between alleles
- Plants that are homozygous for the dominant allele can only made gametes that carry the dominant allele(PP), same goes for homozygous recessive allele (pp)
- When crossed, all offspring of this cross will be heterozygous allele (Pp)
- Can show whether the tested individual is heterozygous or homozygous

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14
Q

What is a monohybrid in Mendel’s Law of Segregation?

A

Cross checks for the dominance relationship between the alleles of a single gene
- Only good for one trait!
Ex.) individuals that are identically heterozygous for one gene, Pp, are crossed

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15
Q

What are the possible outcomes of Mendel’s Law of Segregation?

A

3 out of 4 possible outcomes will include at lease one copy of the dominant allele (3 pink flowers and 1 white flower)
- 1:4 chance that the offspring inherits 2 recessive p alleles

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16
Q

What is the basis for “Law of Segregation”?

A

Each individual that is a diploid has a pair of alleles for a particular trait and each parent passes an allele at random to their offspring

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17
Q

Mendel’s Law of Independent Assortment

A

Follows two characters at the same time; crossing two true-breeding parents differing in two characters produces DIHYBRIDS in F1 generation, heterozygous for both characters
“Each pair of alleles segregates independently of any other pair of alleles during gamete formation”

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18
Q

Dyhybrid

A

Cross between F1 dihybrids, can determine whether two characters are transmitted to offspring together as a unit or independently

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18
Q

What does Mendel’s Law of Independent Assortment apply only to?

A

Genes on different, nonhomologous chromosomes or those are part of the same chromosome

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19
Q

Linked Genes

A

Crossing over does not happen very often between these genes; alleles of these genes stay together during meiosis

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19
Q

When does crossing over occur?

A

Genes that are far enough apart often assort into gametes independently

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19
Q

Linkage Group

A

All of the genes on a chromosome; genes that are REALLY close to each other are said to be linked

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20
Q

Completely Dominant

A

When the allele is completely dominant and shows a dominant allele that masks a recessive allele (ex. eye color)

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21
Q

Incompletely Dominance

A

An allele is not fully dominant over its partner on a homologous chromosome; both are expressed (red x white makes a pink flower)
Produces an intermediate phenotype

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22
Q

Codominance

A

Both expressed at the same time in heterozygotes
Ex.) ABO Blood Typing

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23
Q

Epistasis (Polygenic Inheritance)

A

Occurs when the expression of one gene is modified (masked, inhibited, or suppressed) by the expression of one or more other genes (Human skin color, coat color in labs)

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24
Q

Pleiotropy

A

Type of genetic expression in which one gene affects multiple traits
ex.) sickle cell anemia
Cystic fibrosis

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25
Q

Chromosomal Aberrations and the different types?

A

Chromosome abnormality, anomaly, aberration or mutation is missing, extra or irregular in a chromosomal portion of a DNA
Types:
Aneuploidy, Monosomy, Trisomy, Deletion, Duplication, Inversion

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26
Q

Aneuploidy

A

Occurs when an individual either is missing a chromosome from a pair or has more than two chromosomes of a pair

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27
Q

Monosomy

A

Individual is born with only one sex chromosome (an X)
ex.) Turner Syndrome

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28
Q

Trisomy

A

Has multiple copies of the same chromosome
ex.) Trisomy 21 (down syndrome) has three copies of chromosome 21

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29
Q

Deletion

A

Portion of the chromosome is missing or deleted

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30
Q

Duplication

A

Portion of the chromosome is duplicated, resulting in extra genetic material

31
Q

Inversion

A

Chromosome rearrangement in which a segment of a chromosome is reversed end to end; turned upside down
- Does not involve a loss of genetic information
- Most common inversion seen in humans is on chromosome 9

32
Q

What kind of change is a mutation?

A

Permanent and random change in the DNA

33
Q

Genes

A

Segments of DNA that are transcribed into RNA often to proteins

34
Q

Transcription

A

Process of making RNA from a gene’s worth of DNA; occurs in cytoplasm of bacteria and nucleus of eukaryotes

35
Q

Translation

A

Process of making proteins from mRNA in the cytoplasm of bacteria and eukaryotes

36
Q

What does mRNA do?

A

Carries genetic message from the DNA to the ribosomes to be used to make proteins

37
Q

Codons

A

Triplets of nucleotides that code for 1 specific amino acid in a protein (Genetic message/recipe to make a protein on the DNA)

38
Q

What is the molecule of transcription?

A

RNA polymerase
- Opens the DNA, reads template strand of DNA and builds RNA one base at a time

39
Q

Where does the transcription occur in?

A

Cytoplasm of bacteria and nucleus of eukaryotes

40
Q

What is a promoter or promoter region in Transcription?

A

Is a stretch of DNA in front of, or upstream from the gene to be copied; this is a point at which the RNA polymerase binds

41
Q

What are transcription factors?

A

Proteins in eukaryotes that help assemble RNA polymerase II, the polymerase used in making mRNA

42
Q

What are the 3 stages of transcription?

A

Initiation
Elongation
Termination
I EAT TERMITES

43
Q

What does initiation do in transcription?

A

RNA polymerase binds to promoter upstream from the gene

44
Q

What does elongation do in transcription?

A

Opens up the DNA to get the transcript
- Reads template
- Inserts complementary bases into growing RNA strand
No Primer, helicase or proofreading needed

45
Q

What does termination do in translation?

A

DNA rewinds behind RNA polymerase; at end of the gene the RNA polymerase falls off
- In bacteria mRNA is immediately ready
- In eukaryotes, it must be processed and released from nucleus

46
Q

What is the modification of mRNA after transcription?

A

Eukaryotic cells modify mRNA after transcription; alterations are done at the mRNA ENDS

47
Q

What is modified at mRNA?

A

5’-cap is a modified GUANINE
- Called “cap” because it is at the start or “head” of mRNA
poly A tail is added at 3’ end (50-250 ADENINES)

48
Q

What do the 5’-cap and poly A tail do?

A
  • Help the mRNA leave the nucleus
  • Protect mRNA from degradation in the cytoplasm
  • Help ribosomes attach to the 5’ end of the mRNA
49
Q

What is mRNA splicing? And what does it entail?

A

Introns, which are non-coding segments of mRNA that are removed and degraded
Exons, are coding segments of mRNA that are spliced together to make the final transcript
Spliceosome (ribozyme), is a type of RNA and proteins that cut out the introns and splice together the exons; acts as an enzyme

50
Q

What are the different types of RNA?

A

mRNA, rRNA, tRNA

51
Q

mRNA

A

Messenger RNA codes for making primary structure of a protein

52
Q

rRNA

A

Ribosomal RNA together with proteins make up the ribosomes, protein factories in the cytoplasm

53
Q

tRNA

A

Transfer RNA brings the amino acids to the ribosomes and mRNA

54
Q

What are the two important sequences of tRNA?

A

Anticodon and amino acid binding site
- tRNA is charged in cytoplasm by adding specific amino acid to as binding site

55
Q

Where are ribosomes are located?

A

Rough Endoplasmic Reticulum and in the cytoplasm

56
Q

What are ribosomes made of?

A

rRNA and proteins; a ribozyme

57
Q

What are the large and small subunits?

A

3 Sites:
A- amino acids
P- Peptide
E- Exit

58
Q

How to build a peptide?

A

By the (3) major steps of translation:
1. Initiation
2. Elongation
3. Termination

59
Q

Initiation of Translation: Building a Peptide

A
  1. Small subunit of ribosome binds to mRNA and moves to start codon, usually AUG
  2. Large subunit binds
60
Q

Termination of Translation: Building a Peptide

A

At the stop codon, a release factor enters the A site and the complex dissociates
Stop Codons are UAG, UAA, UGA
- Release factor promotes hydrolysis, adding water to break bonds

61
Q

What is an Operon?

A

Is a unit made up of linked genes which is thought to regulate others genes responsible for protein synthesis

62
Q

What are the parts of an Operon?

A

-Genes
-Promoter; upstream
-Operator, a switch to turn off and turn on genes

63
Q

What is always with its own promoter?

A

Regulatory gene; it transcribes an mRNA and translate this into a protein

64
Q

What is a repressor protein?

A

It sits on the operator and blocks RNA polymerase

65
Q

What is a repressible operon?

A

trp operon, a group of genes that is used, or transcriber, together
- Codes for the components for production of tryptophan
- Characterized in E coli.

66
Q

When is trp operon expressed (turned on) and repressed (turned off)?

A

When tryptophan levels are low
When tryptophan levels are high

67
Q

What regulates the trp operon?

A

trp repressor
- When bound to tryptophan, it blocks expression of the operon

68
Q

What is a Lac Operon?

A

An inducible operon; is an operon required for the transport and metabolism of lactose in E coli. and many other intestinal bacteria

69
Q

What are the 3 lac operon genes?

A

Permease; bring lactose in the cell
- B-galactosidase; to break lactose into glucose and galactose
- Transacetylase; job is unclear

70
Q

Is the lac operon usually on or off? Why?

A

Lactose is not commonly part of the bacteria’s food source, the operon is usually off
- Only when lactose is present is when its turned on

71
Q

What is a CAP protein?

A

Catabolite activator protein binds to the CAP-binging site immediately before promoter
- Helps RNA polymerase to bind to promoter and transcribe lac genes

72
Q

What is the positive gene regulation?

A

Operator is like a dimmer switch to a light
High levels of glucose= lac operon off
Low levels of glucose, lactose present= operon on

73
Q

What are some stages of eukaryotic gene expression?

A

Regulation of Chromatin Structure
- DNA Methylation/Epigenetic Inheritance
- RNA Processing

74
Q

Regulation of Chromatin Structure

A
  • DNA in nucleus wrapped around a complex of 8 histone proteins
    -Tails of these histones hold the DNA tightly preventing transcription
  • When the tails have acetyl groups added, they loosen permitting transcription
75
Q

DNA Methylation/Epigenetic Inheritance

A

Methyl groups added to DNA to stop transcription

76
Q

What is the organization of a typical eukaryotic gene?

A

1 promoter/1 gene
Promoter, regulatory promoter, enhancer region, activator proteins

77
Q

Dimmer

A

Noncoding DNA; that act as simmer switches controlling transcription

78
Q
A

Cell Biology Test 3 (3 decks)

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