Test 3 Flashcards
1
Q
Nature of DNA in Eukaryotic Organisms
A
- in shape of high coiled linear chromosomes
- 46 chromosomes in humans
- 2 meters of DNA coiled in nucleus
2
Q
What are chromosomes composed of?
A
- chromatin (protein DNA complex)
3
Q
Characteristics of Chromosomes (in humans)
A
- 23 distinct shapes/types
- 2 chromosomes of each tyoe (Type A - Type W)
- 2 complete sets of 23
- 23 paternal chromosomes
- 23 maternal chromosomes
4
Q
A(paternal) & A(maternal)
A
- homologous chromosomes
- contain the same gene
- not genetically identical
- same gene, different version
5
Q
Allele
A
different versions of the same gene
6
Q
Ploidy
A
the number of sets of chromosomes
ex:
diploid - 2 sets
haploid - 1 set
triploid - 3 sets
7
Q
Haploid Number
A
the number of chromosomes in a complete set
8
Q
Cell cycle
A
events between formation of cell and division of cell
1. interphase (majority of the cell cycle)
2. mitosis (nuclear division)
3. cytokinesis (cytoplasmic division) (goes back to interphase)
9
Q
zygote formation
A
egg (haploid) + sperm (haploid) = zygote (diploid)
10
Q
How many stages does interphase have?
A
3:
1. Gap 1 (G1)
2. S (synthesis)
3. Gap 2 (G2)
11
Q
Gap 1
A
- cell growth
- normal cell stuff
- enzyme production (necessary for DNA replication
12
Q
What is G0?
A
cells that never exit G1
cells that never divide
13
Q
S stage
A
- chromosomes replicate
- MTOC replicates centrioles (MTOC is replicated)
- dyad is created
14
Q
Dyad
A
- pair of sister chromatids (identical)
- held together by a centromere that contains a kinetochore
15
Q
Centromere
A
structure in a chromosome that holds 2 sister chromatids together
16
Q
Kinetochore
A
protein that forms on a chromatid during cell division that allows it to attach to a spindle fiber on a chromosome
17
Q
Gap 2 (G2)
A
- mitochondria/chloroplasts divide
- massive production of tubulin
- chromosomes start to coil more
18
Q
How many phases are in mitosis?
A
5
19
Q
Prophase
A
- chromosomes become completely condensed
- centrioles move to opposite ends of the cell
a. produces polar microtubules (connects the centrioles and will pull the chromosomes apart)
b. produces aster fibers (connects centrioles to cell membrane)
20
Q
Prometaphase
A
- nuclear membrane degenerates
- MTOCs provide kinetochore microtubules (connects chromosomes to microtubules)
21
Q
Metaphase
A
- kinetochore microtubules arrange dyads in an independent assortment manner in the center of the cell
a. this is the metaphasic plate
22
Q
Anaphase
A
- centrosomes break apart
- chromatids get pulled towards opposite ends of cell
- polar microtubules lengthen so the cell lengthens
- spindle apparatus; microtubules involved in mitosis (polar, aster, kinetochore)
23
Q
Telophase and Cytokinesis
A
- chromosomes reach end of the cell
- nuclear envelope forms
- spindle apparatus disappears
- chromosomes de-condense
- belt of actin around metaphasic plate constricts and pinches cell in half
- cleavage furrow forms (in animal cells)
24
Q
Gametogenesis
A
- cells undergo meiosis to form gametes
25
Prophase 1
- same as in mitosis
PLUS
- homologous chromosomes hydrogen bond to each other to create a tetrad (bivalent)
- 23 tetrads at the end of prophase 1
26
Bivalent
a pair of homologous chromosomes (4 chromatids)
27
Synapse
the pairing of homologs
28
Crossing over
- homologous chromosomes exchange segments with each other
- occurs 50-70 times per bivalent
- responsible for genetic variability
29
Metaphase 1
- same as mitosis
- kinetochore microtubules arrange dyads in in the center of the cell
a. this is the metaphasic plate
30
Anaphase 1
- homologs separate and dyads are pulled to opposite ends
31
Telophase 1 and Cytokinesis
- same as in mitosis EXCEPT:
1. nuclear membrane does not reform
2. chromosomes stay condensed
32
Independent Assortment
- random orientation of homologs at the metaphasic plate
- parental sets of chromosomes do not stay together through meiosis 1
33
Meiosis 2
Prophase 2 - same as mitosis
Metaphase 2 - same as mitosis (23 dyads instead of 46)
Anaphase 2 - same as mitosis (23 dyads instead of 46)
Telophase 2 and Cytokinesis - same as mitosis
34
What is the result of gametogenesis?
Gametes
35
What is a polar body?
little haploid bags of chromosomes
36
Why is the egg that is produced in oogenesis so large?
Egg must be large enough to provide nutrients for 5 days
-occurs in a protective environment
37
Plant cell divison
- no centrioles in MTOC
- no aster fibers
- cytokinesis occurs through cell plate formation
- division starts in middle and spreads outward
38
Gene pair
2 copies of the same gene on homologous chromosomes
39
Locus
physical location of a gene on a chromosome
40
Dominant allele
allele that is always fully expressed when present
41
Recessive allele
only expressed if gene pair consists of 2 versions of that allele
42
Homozygous pair
gene pair that consists of the same alleles
43
Heterozygous pair
gene pair that consists of different alleles
44
Genotype
allele make-up of gene pair
45
phenotype
physical expressions of the genotype
46
Mendelian genetics
the study of inheritance
47
Facts about Mendel
- studied in a monostery as a monk
- was a mathmetician
- studied inheritance of 7 traits in pea plants
48
Monoecious
- have both female and male reproductive parts
- able to self-fertilize
49
Monohybrid Crosses
- true breeding crossing
- phenotype ratio is 3:1
50
Truebreeding
- produces offspring of the same phenotype
51
Mendel's 1st Law / Principle of Segregation
- individuals have 2 factors (alleles) for each trait
- factors segregate during gamete formation so that each gamete only gets one of those factors
- deduced the diploid nature of eukaryotic organisms (meiosis)
- 3:1 ratio for the offspring of heterozygotes
52
Dyhybrid Crosses
- 9 genotypes
- 4 phenotypes
- 9:3:3:1
53
What explains why dihybrid and monohybrid crosses works?
- any sperm is equally likely to fertilize an egg
54
Mendel's 2nd Law
- law of independent assortment
- traits are inherited independently of each other because of independent assortment
55
How did Mendel get "lucky"?
- all traits for the peas were on separate chromosomes
- all traits for the peas only had 2 alleles
- all traits for the peas were controlled by one gene
56
Linkage
- genes for 2 traits on the same chromosome
- genes are inherited dependently
- only way to stop linkage is by crossing over
57
Incomplete Dominance
- the dominant allele does not completely suppress expression of recessive allele
- ex: four o'clock flower
58
Co-dominant Alleles
- both alleles are fully expressed in a heterozygote
- ex: bloodtype
59
What does blood type depend on?
- the presence or absence of certain proteins (antigens)
60
Blood types: phenotype, genotype, and allele
A , I^A I^A, I^A
B, I^B I^B, I^B
AB, I^A I^B
O, ii, i
61
Epistasis
- one gene controls the expression of another
- ex: golden retrievers
62
Polygenic Traits
- a trait that is influenced by more than one gene
- ex: height
63
Pleiotropy
- a gene that influences more than one trait
- ex: sickle cell anemia
64
Traits of Sickle Cell Anemia
- a sickle cell lives for 30 days compared to a healthy cell that lives for 4 months
- sickle cells clump together, cannot move easily through blood vessels, and inhibit circulation
65
What causes sickle cell anemia?
it is caused by recessive mutation of 1 hemoglobin gene
66
What is hemoglobin?
- a quaternary protein structure of 4 proteins (contains iron)
- facilitates the transportation of oxygen in red blood cells
67
Aneuploidy
- number of chromosomes is not a multiple of the haploid number
- extra or missing chromosome
- tricomy (3 different chromosomes of the same type)
- monosomy (1 type of chromosome
68
Errors in Meiosis
Non-disjunction (2 types)
- aneuploidy
- polyploidy
69
Non-disjunction
some or all homologous pairs fail to separate during Meiosis 1
70
Polyploidy
the condition of possessing more than two complete sets of chromosomes
71
How many pairs of chromosomes are homologs in mammals?
22 pairs of chromosomes are autosomal / homologs
72
How many pairs of chromosomes are sex chromosomes?
1 pair of chromosomes
73
X chromosome
- largest chromosome
- contains genes for both male and female traits
74
Y chromosome
- smallest chromosome
- 70 genes
- SRY gene (epistatic over other sex genes)
75
Sex linked traits
- non-gender specific traits that are carried on the x chromosome
- ex: color-blindness,
76
Molecular Genetics
the study of function and structure of DNA and RNA
77
What is DNA and RNA?
polymers of nucleotides
78
H or OH bond on 2nd carbon on nitrogenous base
H bond = DNA
OH bond = RNA
78
What does DNA stand for?
deoxyribonucleic acid
79
What does RNA stand for?
ribonucleic acid
80
What are the two types of nitrogenous bases?
Purines and Pyrimidines
81
Purines
Adenine and Guanine (both are present in DNA and RNA)
82
Pyrimidines
Cytosine (in both RNA and DNA)
Uricil (only in RNA)
Thymine (only in DNA)
83
How many nucleotide are in 46 chromosomes (one cell)
# of A = # of T
12 billion
# of A = # of T
# of G = # of C
84
What kind of arrangement does DNA have?
anti parallel
85
Complementary base pairing
- the manner in which nitrogenous bases align with each other
- A & T
- G & C
86
What is DNA's main jobs?
1. replicates (in S phase)
2. codes for RNA
87
DNA replication
- starts at origin of replication (OR)
88
Proteins involved in DNA replication
- helicase
- topoisomerase
- RNA primase
- DNA polymerase III
- DNA polymerase I
- DNA ligase
89
Helicase
- separates the 2 DNA strands
- moves from 3' to 5'
90
Topoisomerase
- moves ahead of helicase
- uncoils the chromosome
91
RNA Primase
- lays down RNA primer and adds RNA nucleotides to exposed DNA
92
DNA polymerase III
- adds DNA nucleotides to exposed DNA nucleotides
93
DNA polymerase I
- replaces RNA nucleotides with DNA nucleotides
94
DNA ligase
- joins okazaki fragments together
95
semi-conservative replication
- DNA replication model in which the new DNA strand contains one original strand one one new strand (new strands are sister chromatids)
- formation of dyads
96
DNA replication steps
1. helicase separates the DNA strands
2. topoisomer binds ahead of helicase and uncoils the chromosome
3. RNA primase adds RNA primer at OR
4. DNA poly 3 binds at Or and adds DNA nucleotides
5. DNA poly 1 replaces RNA primase with DNA nucleotides
6. DNA ligase joins Okazaki fragments together
97
Okazaki fragments
- short strands of DNA that make up the lagging strand during DNA replication
98
What is the end result of DNA replication
46 dyads
99
j
100
2 Steps of Protein Synthesis
1. Transcription
2. Translation
101
Transcription
- process where information for a gene is used to build an RNA (DNA nucleotides to RNA nucleotides)
102
Steps of transcription
1. a transcription factor binds to the chromosome upstream of promoter site
2. step one allows RNA polymerase to bind to promoter site and transcribe the gene
3. RNA polymerase moves down gene, separates strands, and adds free nucleotides to one of the exposed strands (3' to 5')
4. RNA polymerase reaches the terminator site, RNA polymerase and RNA detaches. DNA strands reattach and recoil
5. RNA transcript is floating around the nucleoplasm
103
Promoter site
- sequence of nucleotides that occurs 40 base pairs upstream of gene
- contains a TATA box
104
Terminator site
- sequence of nucleotides that signals end of gene
105
3 Types of RNA
1. Ribosomal RNA (rRNA)
2. Messenger RNA (mRNA)
3. Transfer RNA (tRNA)
106
Ribosomal RNA
- component of a ribosome
- goes to nucleolus to produce ribosomes
107
Messenger RNA
- linear RNA strand that contains a code for producing a protein
- all mRNAs start with AUG
- leaves nucleus into cytoplasm
108
Codon
- 3 nucleotide sequence on mRNA that codes for a specific amino acid
109
Start Codon
- AUG
- codes for methionine
- signals the start of translation
110
DNA triplet
- 3 nucleotide sequence on DNA that codes for a specific amino acid
111
Stop codon
- signals the stop of translation
112
Transfer RNA (tRNA)
- folded RNA that carries amino acids from the cytoplasm to the ribosome so a protein can be built
- different tRNA for every amino acid
113
How many possible anticodons and codons are there?
61 possible anticodons
64 possible codons
114
Anticodon
- bonds to the codon
- 3 RNA nucleotide sequence that binds to the codon
- ex:
a. codon - UAU
b. anticodon - AUA
c. DNA triplet - ATA
115
What is the origin of replication?
- small base pair sequences in a chromosome that binds to the enzyme that starts replication
116
Steps of Translation
1. Initiation
2. Chain elongation
3. Termination
117
Initiation
- the ribosome attaches to the mRNA and the initiator, tRNA w/ its amino acids binds to the mRNA
- called the initiation complex
118
Chain Elongation
- once initiation complex forms, the ribosome exposes the next codon
- the correct tRNA w amino acid binds to that codon
- the ribosome forms a peptide bond between the 2 amino acids
- the ribosome shifts down, exposes the next codon while the first tRNA detaches from its amino acid and from ribosome
119
3. Termination
- ribosome reaches the stop codon (no tRNA for stop codon)
- a releasing factor (protein) binds to stop codon and causes the ribosome, mRNA, and protein to all separate
- result is a polymer of amino acids
120
Gene amplification
- may be more than 1 copy of a gene on a chromosome
- multiple simultaneous transcription of each gene
- multiple simultaneous translation of each RNA
121
Gene
a section of chromosome that codes for an RNA molecule
122
Coding gene
- codes for mRNA / protein
123
Non-coding gene
- codes for non mRNA RNA
124
Post-Transcription Modification
- Polyadenylation
- Splicing
- Alternative Splicing
125
Polyadenylation
- adenines are added to end of mRNA
126
Splicing
- removal of introns from mRNA
127
Alternative Splicing
- splicing of an mRNA in different ways to produce different proteins
128
Intron
- noncoding sections of an RNA transcript
129
Exon
- coding sections of an RNA transcipt
130
What percent of the human genome are genes?
2%
131
Psuedogene (vestigal gene)
- genes that were once functional, but due to some mutation they can no longer function
132
GULD
- gene that is found in all mammals
- allows for the biosynthesis of vitamin c
- non-functional in primates
133
What percent of DNA is endogenous retrovirus DNA?
8%
134
Endogenous retrovirus
non-functional provirus
135
Virus
- protein encased capsule of DNA or RNA capable of infecting cells and reproducing in those cells
136
2 Types of Virus
- DNA virus
- Retrovirus
137
DNA virus
injects DNA that is transcribed and translated to make more virus
138
Retrovirus
- injects mRNA and that undergoes reverse transcription
- DNA is inserted into the host's DNA
- in most cases it is dormant
- expressed under certain conditions
139
Reverse transcription
mRNA to DNA
140
Provirus
- viral DNA incorporated into host's DNA
