Bi 112 review Flashcards
During metaphase humans have how many chromosomes?
46
When not actively dividing, what phase are cells arrested in?
G0 phase
What phase are chromosomes most condensed in?
Metaphase
How many homologous chromosomes do humans have?
23
At the end of metaphase how many chromosomes do humans have?
46
_______ & _______ can disturb the cell cycle when they are mutated.
Tumor-suppressors and proto-onco genes.
A human that is XO (missing a sex chromosome) is:
2n-1=46
Down syndrome is “2n+1=47”
Cells that are “2n+1” are called _____ and cause ________.
Trisomic (have an extra chromosome)
And cause Down syndrome
Somic=1 extra chromosome
Cells that are triploid are:
3n (have an extra SET of chromosomes)
Can’t have offspring
Ploid=sets
How does cytokinesis occur in plants?
The cell plate forms between nuclei (by vesicles)
What is the primary checkpoint for external signal influence?
(Double check this one)
G1/S checkpoint
What checkpoint does the cell make a commitment to complete mitosis?
(Double check)
G2/M
Cereal grains have __ sets of chromosomes.
6n
Strawberries have ___ sets of chromosomes.
8n
____ is the point of constriction of chromosomes
Centromere
In what phases of interphase can the nucleolus be seen?
ALL
Sperm and eggs have ___ sets of chromosomes
n (1n)
1/2 the amount of genetic material
In what phase is genetic material duplicated?
S-phase of interphase
How many sets of chromosomes do human cells have?
2n
Uncontrolled checkpoints in the cell cycle can cause ________
CANCER!
On the average chromosome there are ______ crossing over events.
2-5
In what phase of mitosis does the nucleolus disappear?
Prophase
In what phase do chromosomes move to center of the cell through associated protein “motors”?
Pro-metaphase
What is the longest phase (primary growth) in interphase?
G1
In mitosis how Many chromosomes in a human cell after interphase?
(Double check)
46
When does non-disjunction occur?
When nonsister chromatids fail to separate
Failure of chromosomes to move to opposite poles during either meiotic division
Gametes produced from Nondisjunction in meiosis1 and meiosis 2.
Meiosis-1: n+1,n+1,n-1,n-1
Meiosis-2: n+1,n-1,n,n
Homologous chromosomes “zipper together”:
Synapsis (crossing over occurs between nonsister chromatids)
Occurs in prophase 1 in meiosis 1
Microtubules of spindle shorten and (chiasmata break) in ________.
Anaphase 1
Sister chromatids remain attached, homologues separate and move to opposite poles
What is “reductive division” and when does it occur?
In meiosis 1.
It is the “first meiotic division”. Results in daughter cells that contain one homologue from each chromosome pair.
Diploid—>Haploid
What is worse, Nondisjunction at meiosis 1 or meiosis 2?
Meiosis 1, because both daughter cells will be diploid?
(2 will have an extra chromosome, 2 will be missing a chromosome)
all gametes will be affected
The site of chromosome crossover is called _______.
Chiasmata
What happens in anaphase II?
Sister chromatids separate and chromosomes move toward opposite poles.
(Microtubules shorten, centromeres split, sister chromatids pulled to opposite poles)
Why must a cell undergo meiosis?
Sexual reproduction (exchanges genetic material) Producing non-identical haploid cells (diploid–>haploid)
How many chromosomes in humans after metaphase 1?
23
Tetrad:
4 chromatids attached (one unit)
-composed of two nonsister chromatids (4 total)
During meiosis, chromatids remain attached during:
Prophase1 and Metaphase1
Separate in anaphase1
How many microtubules are attached per tetrad?
2 (one for each sister chromatid)
In meiosis, how many chromosomes after anaphase1? (Humans)
46
Aneuploid gametes:
Gametes with missing or extra chromosomes
Conditions caused by Aneuploid gametes include:
Turner Syndrome, Jacob’s Syndrome, Down Syndrome
Difference between mitosis and meiosis:
Mitosis-identical diploids (body cells/somatic)
Meiosis-non-identical haploid cells
How many chromosomes after telophase2?
23 (1/2 the amount of genetic makeup)
How would a women go her entire life without knowing she is XXX?
“Barr Bodies”
-no syndrome present/unable to produce offspring-
How do chromosomes migrate to their respective poles?
By microtubules shortening
How many daughter cells after meiosis2?
4 (4 1n – 1 set of chromosome each)
Why can a 4n cell produce, but not 3n?
Unequal separation of chromosomes. Needs to be even number for pairing.
How many human chromosomes at the end of prophase1?
23
In what phase do tetrads line up at the equator of the cell?
Metaphase1
Operative word= “tetrads”
Only case in which humans can survive w/ less than 46 chromosome:
Down Syndrome
True Breeder:
always passes down a certain phenotypic trait to its offspring. Same phenotype over multiple generations.
(Self fertilizing plants)
In meiosis, allele segregation occurs during ______.
Anaphase.
Polygenic inheritance:
Occurs when multiple genes are involved in controlling the phenotype of a trait.
(When multiple genes control 1 trait)
-ex. Human height/skin color-
When does Mendel’s principle of segregation occur?
During anaphase of meiosis.
Alleles remain discrete/no blending
-separate-
Pleiotropy
Refers to an allele which has more than one effect on the phenotype
(Cystic fibrosis and sickle cell anemia)
-multiple symptoms can be traced to on defective allele-
Pleiotropy is difficult to predict because _________.
A gene that affects one trait often performs other, unknown functions
Genotype:
Total set of alleles an individual contains.
Genetic makeup
Phenotype:
Physical appearance
Physical expression of genes
What effects skin color?
Environment
A _________ examines 2 separate traits in a single cross.
Dihybrid Cross.
Monohybrid-2 variations of a single trait
What is it called when a heterozygote shows some aspect of phenotype of both homozygotes?
Codominance (type AB blood)
I-a and I-b are dominant to i, but co dominate to eachother
What is the probability of landing heads 4x in a row?
1/16
1/2x1/2x1/2x1/2=1/16
When does Mendel’s principle of independent assortment occur?
During metaphase
Incomplete dominance:
Heterozygote is intermediate in phenotype between 2 homozygotes
(Red flower x white flowers=pink flowers)
Probability of boy, boy, boy, boy, girl?
1/32
1/2x1/2x1/2x1/2x1/2=1/32
A monohybrid cross examines:
One trait (ex. Flower color)
What is a Punnett square simulating?
Segregation of alleles and fertilization.
In cats, black and orange fur color is caused by an x-linked allele. The heterozygote is tortoiseshell. What kinds of offspring would you expect from cross of a black female and orange male?
Tortoiseshell females; black males
Color blind woman marries a non-color blind man. All of their sons, but none of their daughters are color blind. Explain.
The gene for color vision is linked to the X chromosome.
Eye color is an x-linked trait in flies. White eyed female x red eyed male will produce what genotype sand phenotypes in males and females?
Females- red eyed, but all carriers
Males- all white eyed
Can male cats be tortoiseshelled?
Yes, XXY.
What is the gene on the Y chromosome that makes a man a man?
SRY gene on Y
Default for humans is female
How many homologous pairs of chromosomes do female and make humans have?
Females 23, males 22
22 pairs are autosomes
1 pair o sex chromosomes
In human females, what happens during meiosis to the sex chromosomes during prophase1? What happens to males?
Eggs undergo crossing over. Males do not have a pair of homologous sex chromosomes so they don’t go through Synapsis.
Why do males inherit all genes on the x-chromosome from their mothers?
Because they only have one x-chromosome
Why are males more related to their mothers? Why are females?
Males get the genes on the x-chromosome from their mothers. Both males and females obtain mitochondrial DNA from their mothers.
What are non-sex chromosomes called?
Autosomes
When did Nondisjunction occur if you have 2 cells that are n-1 and 2 cells that are n+1? (At conclusion of meiosis)
Meiosis I
If during meiosis II, 2 normal, 2 defective
What type of sampling collects cells from the placenta for examination?
Chronic villi sampling
Genomic imprinting
Phenotype exhibited by a particular allele depends on which parent contributed the allele to the offspring
(Balances out expression of genes by expressing particular allele)
Why would scientists assume that people that are XYY would be more aggressive than XY?
In XYY, y-chromosomes are not condensed, so they would have 2 functioning Y chromosomes (more testosterone?)
Trisomy 21 is _________
Down Syndrome
XXY is ______
Klinefelter syndrome (males)
XO is _______
Turner syndrome (females)
XYY is _______
Jacob syndrome (more aggressive)
OY is _______
A non viable zygote.
Females do not express both X chromosomes because:
One X chromosome becomes a “Barr Body”
Why do humans that are XXY still have female characteristics?
The X chromosome is not completely inactivated.
Most x linked disorders are _____
Systematic
How are some women mosaics for color blindness?
X genes are inactivated. Mosaics have a portion of the normal X chromosome inactivated and the other portion has the has the one w/ the mutation
Allele
Alternative form of a gene
Allele segregation occurs during _____
Meiosis
Genotypic and phenotypic ratio of 2 pink Japanese 4 o’clocks:
1 (RR): 2 (RW): 1 (WW)
Mendel’s classic Dihybrid cross, what is the expected phenotypic ratio?
9:3:3:1
Epistasis:
Behavior of gene products can change the ratio expected by independent assortment (even if genes are on different chromosomes that don’t exhibit independent assortment)
(Ex. Corn/lab coat color)
Transcription direction
5—>3 prime end
Enzyme that catalyses transcription:
RNA polymerase
Transcription in prokaryotes occurs _________
In the cytoplasm
Adds amino acid to tRNA
Aminoacyl-tRNA synthetase (enzyme)
Enzyme that adds sequence of adenine to end of mRNA, protecting is from degradation:
Poly-a polymerase
Wobble pairing:
Allows less stringent pairing betw. 3’ base of codon
Where does translation take place?
Cytoplasm and rough er
Why are prokaryotes able to start translation before transcription ends?
No nucleus
Transcription outside of the nucleus occurs where?
Mitochondria
Transcription occurs in the nucleus
A 36 nucleotide sequence will direct the production of:
A polypeptide that consists of 11 amino acids
36/3=12… Stop codon doesn’t code for amino acid
A mutation where part of the chromosome is moved to a new location:
Translocation
List the 3 sites on a ribosome (in order)
E,P,A
Why are humans so complex with so few genes?
Alternative splicing
Enzymatic component of ribosomes, what does it do, where is it located?
Peptidyl transferase, forms peptide bonds, large subunit
Synthesis of ribosomal RNA (rRNA) occurs in ________
Nucleolus
RNA polymerase binds to a _______ where the a-helix unwinds and transcription starts.
A promoter
Peptidyl transferase
The enzymatic component of ribosome
Mega complex that cuts introns and glues exons:
Splicesome
DNA—>RNA—>protein
Dna–>RNA =transcription
RNA–>protein =translation
Karyotype
A karyotype is a picture of an individual’s chromosomes. Karyotypes can tell the gender of an individual (like male or female) and whether or not they have specific genetic disorders related to chromosome mutations.
The process by which the cytoplasm of a eukaryotic cell divides to produce 2 cells is called:
Cytokinesis
Prior to mitosis, each chromosome of a eukaryotic cell consists of a pair of identical structures called _________
Sister chromatids
Which phase of mitosis is described as sister chromatids separate and move to the respective pole?
Anaphase
During which phase are sister chromatids considered full fledged chromosomes?
Anaphase
The transfer of genetic information from DNA to RNA is called
Transcription
Translation occurs where in eukaryotic cells?
Cytoplasm, rough er, mitochondria, ribosomes (all of the above)
Transcribe DNA: TATCCGGTA
TATCCGGTA
AUAGGCCAU
Adenine gets paired w/ uracil instead of thyamine.
The directions for each amino acid in a polypeptide are indicated by a codon that consists of ____ nucleotides in a RNA molecule.
3
There are how many total codons?
64
There are ___ codons that code for amino acids and ___ kinds of amino acids.
61,20
There are 61 codons that code for amino acids and 20 kinds of amino acids
