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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
Codominance
Both expressed at the same time in heterozygotes Ex.) ABO Blood Typing
23
Epistasis (Polygenic Inheritance)
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)
24
Pleiotropy
Type of genetic expression in which one gene affects multiple traits ex.) sickle cell anemia Cystic fibrosis
25
Chromosomal Aberrations and the different types?
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
26
Aneuploidy
Occurs when an individual either is missing a chromosome from a pair or has more than two chromosomes of a pair
27
Monosomy
Individual is born with only one sex chromosome (an X) ex.) Turner Syndrome
28
Trisomy
Has multiple copies of the same chromosome ex.) Trisomy 21 (down syndrome) has three copies of chromosome 21
29
Deletion
Portion of the chromosome is missing or deleted
30
Duplication
Portion of the chromosome is duplicated, resulting in extra genetic material
31
Inversion
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
What kind of change is a mutation?
Permanent and random change in the DNA
33
Genes
Segments of DNA that are transcribed into RNA often to proteins
34
Transcription
Process of making RNA from a gene's worth of DNA; occurs in cytoplasm of bacteria and nucleus of eukaryotes
35
Translation
Process of making proteins from mRNA in the cytoplasm of bacteria and eukaryotes
36
What does mRNA do?
Carries genetic message from the DNA to the ribosomes to be used to make proteins
37
Codons
Triplets of nucleotides that code for 1 specific amino acid in a protein (Genetic message/recipe to make a protein on the DNA)
38
What is the molecule of transcription?
RNA polymerase - Opens the DNA, reads template strand of DNA and builds RNA one base at a time
39
Where does the transcription occur in?
Cytoplasm of bacteria and nucleus of eukaryotes
40
What is a promoter or promoter region in Transcription?
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
What are transcription factors?
Proteins in eukaryotes that help assemble RNA polymerase II, the polymerase used in making mRNA
42
What are the 3 stages of transcription?
Initiation Elongation Termination I EAT TERMITES
43
What does initiation do in transcription?
RNA polymerase binds to promoter upstream from the gene
44
What does elongation do in transcription?
Opens up the DNA to get the transcript - Reads template - Inserts complementary bases into growing RNA strand No Primer, helicase or proofreading needed
45
What does termination do in translation?
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
What is the modification of mRNA after transcription?
Eukaryotic cells modify mRNA after transcription; alterations are done at the mRNA ENDS
47
What is modified at mRNA?
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
What do the 5'-cap and poly A tail do?
- Help the mRNA leave the nucleus - Protect mRNA from degradation in the cytoplasm - Help ribosomes attach to the 5' end of the mRNA
49
What is mRNA splicing? And what does it entail?
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
What are the different types of RNA?
mRNA, rRNA, tRNA
51
mRNA
Messenger RNA codes for making primary structure of a protein
52
rRNA
Ribosomal RNA together with proteins make up the ribosomes, protein factories in the cytoplasm
53
tRNA
Transfer RNA brings the amino acids to the ribosomes and mRNA
54
What are the two important sequences of tRNA?
Anticodon and amino acid binding site - tRNA is charged in cytoplasm by adding specific amino acid to as binding site
55
Where are ribosomes are located?
Rough Endoplasmic Reticulum and in the cytoplasm
56
What are ribosomes made of?
rRNA and proteins; a ribozyme
57
What are the large and small subunits?
3 Sites: A- amino acids P- Peptide E- Exit
58
How to build a peptide?
By the (3) major steps of translation: 1. Initiation 2. Elongation 3. Termination
59
Initiation of Translation: Building a Peptide
1. Small subunit of ribosome binds to mRNA and moves to start codon, usually AUG 2. Large subunit binds
60
Termination of Translation: Building a Peptide
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
What is an Operon?
Is a unit made up of linked genes which is thought to regulate others genes responsible for protein synthesis
62
What are the parts of an Operon?
-Genes -Promoter; upstream -Operator, a switch to turn off and turn on genes
63
What is always with its own promoter?
Regulatory gene; it transcribes an mRNA and translate this into a protein
64
What is a repressor protein?
It sits on the operator and blocks RNA polymerase
65
What is a repressible operon?
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
When is trp operon expressed (turned on) and repressed (turned off)?
When tryptophan levels are low When tryptophan levels are high
67
What regulates the trp operon?
trp repressor - When bound to tryptophan, it blocks expression of the operon
68
What is a Lac Operon?
An inducible operon; is an operon required for the transport and metabolism of lactose in E coli. and many other intestinal bacteria
69
What are the 3 lac operon genes?
Permease; bring lactose in the cell - B-galactosidase; to break lactose into glucose and galactose - Transacetylase; job is unclear
70
Is the lac operon usually on or off? Why?
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
What is a CAP protein?
Catabolite activator protein binds to the CAP-binging site immediately before promoter - Helps RNA polymerase to bind to promoter and transcribe lac genes
72
What is the positive gene regulation?
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
What are some stages of eukaryotic gene expression?
Regulation of Chromatin Structure - DNA Methylation/Epigenetic Inheritance - RNA Processing
74
Regulation of Chromatin Structure
- 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
DNA Methylation/Epigenetic Inheritance
Methyl groups added to DNA to stop transcription
76
What is the organization of a typical eukaryotic gene?
1 promoter/1 gene Promoter, regulatory promoter, enhancer region, activator proteins
77
Dimmer
Noncoding DNA; that act as simmer switches controlling transcription
78

Cell Biology Test 3 (3 decks)

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