Exam 3 Flashcards
Define Mitosis
The division of the nucleus
Define cytokinesis
The division of the cytoplasm
Define Meiosis
Gametes production by a variation of cell division
During what phase of the cell cycle does replication occur?
S phase
What are the main phases of mitosis?
Interphase Prophase Metaphase Anaphase Telophase
What are main phases of mitosis?
Interphase Prophase Metaphase Anaphase Telophase
What occurs during Interphase?
Chromosomes duplicate and have not yet condensed.
What occurs during prophase?
- Chromatin fibers become tightly coiled
- Chromosomes become visible
- Nuclear envelope fragments
- Mitotic spindle begins to form
What occurs during metaphase?
Chromosomes convene on the metaphase plate
Which mitotic phase is the longest phase?
Metaphase
What occurs during Anaphase?
2 sister chromatids separate
What occurs during Telophase
2 daughter nuclei begin to form (cleavage furrow)
During anaphase, what do sister chromatids do?
Thet separate and move along kinetochore microtubules toward oposite ends of the cell
How do microtubules shorten?
By depolymerizing at their kinetochore ends
Which of the following occurs during prophase?
The mitotic spindle begins to form
What is the average amount of time for a human cell to undergo one division?
24 hours
How long is each phase of cell division in a human cell?
G1= 6 hours
S= 12 hours
G2= 6 hours
Mitotic phase=
How long is metaphase?
20 mins
How long is anaphase?
3 mins
Where did Mitosis evolve from?
Binary Fission
Where did Mitosis evolve from?
Binary Fission
Where did Mitosis evolve from?
Binary Fission
What type of cell division do protists experience?
cell division intermediate between binary fission and mitosis
True or False: The frequency of cell division varies with the type of cell
False
Do human skin cells divide frequently or infrequently?
Frequently
True or false: Mature nerve and muscle cells don’t divide in a mature human
True
What is a good analogy for the cell cycle control system?
Stoplights or a clock
How is the Cell cycle controlled?
The clock has specific checkpoints where the cell cycle stops until a go-ahead signal is received
What is the most important checkpoint?
G1
What happens if a cell receives a go ahead at the G1 checkpoint?
It will complete the S, G2, and M phases and divide
What happens if a cell does not recieve a go ahead at the G1 checkpoint?
It will exit the cycle switching into a nondividing state called the G0 phase
True or False: Most cells of the human body are actually in the G0 phase
True
True or False: Most cells of the human body are actually in the G0 phase
True
What is an example of an internal signal (occuring at the M phase check point)?
Kinetochore’s not attached to spindle
Microtubules send a molecular signal that delays anaphase
What are external signals?
Growth factors, proteins released by certain cells that stimulate other cells to divide
What do external signals allow cells to do?
Pass the G1 checkpoint and divide
What does the Platelet derived growth factor (PDGF) do?
Stimulates the division of human fibroblast cells in culture
What is another example of an external signal and what occurs?
Density-Dependent Inhibition
Crowded cells stop dividing
What is another example of an external signal and what occurs?
Density-Dependent Inhibition
Crowded cells stop dividing
What is anchorage dependence?
Animal cells must be attached to a substratum in order to divide
Do cancer cells exhibit density dependent inhibition or anchorage dependence?
Neither
Do cancer cells respond normally to the body’s control mechanisms? (go through checkpoints)
No
Do cancer cells need growth factors to grow and divide? Why/why not?
- No.
- They make their own growth factor
- They may convey a growth factor’s signal without the presence of the growth factor
- They may have an abnormal cell cycle control system
How is a normal cell converted to a cancerous cell?
A process called transformation
How are tumors formed?
Cancer cells that are not eliminated by the immune system accumulate
What is a tumor?
Masses of abnormal cells within otherwise normal tissue
What is a benign tumor?
When abnormal cells remain only at the original site
What is a malignant tumor?
Abnormal cells invade surrounding tissues and may form additional tumors
What is metastasize?
Exportation of cancer cells to other parts of the body
What is metastasize?
Exportation of cancer cells to other parts of the body
Define asexual reproduction
a single individual passes genes to its offspring without the fusion of gametes
What is a clone?
A group of genetically identical individuals from the same parent
Define sexual reproduction
two parents give rise to offspring that have unique combinations of genes inherited from the two parents
In an ovum, how many autosomes, x chromosomes, y chromosomes are there and is it haploid/diploid?
- 22 autosomes
- 1 x chromosomes
- 0 y chromosomes
- haploid (n)
In a sperm how many autosomes, x chromosomes, y chromosomes are there and is it haploid/diploid?
- 22 autosomes
- 0 or 1 x chromosomes
- 0 or 1 y chromosomes
- haploid (n)
In a female somatic cell, how many autosomes, x chromosomes, y chromosomes are there and is it haploid/diploid?
- 22 pairs
- 2 x chromosomes
- 0 y chromosomes
- Diploid (2n)
In a male somatic cell, how many autosomes, x chromosomes, and y chromosomes are there, and is it haploid/diploid?
- 22 pairs
- 1 x chromosome
- 1 y chromosome
- diploid (2n)
In a zygote, how many autosomes, x chromosomes, and y chromosomes are there, and is it haploid/diploid?
- 22 pairs
- 1 or 2 x chromosomes
- 0 or 1 y chromosome
- Diploid (2n)
In a zygote, how many autosomes, x chromosomes, and y chromosomes are there, and is it haploid/diploid?
- 22 pairs
- 1 or 2 x chromosomes
- 0 or 1 y chromosome
- Diploid (2n)
A human cell containing 22 autosomes and a y chromosome is a
Sperm cell
Plants and algae exhibit a
alternation of generations
In plants and algea the life cycle includes how many multicellular generations/ stages and what are they?
2
One diploid one haploid
What is the name of the diploid organism in plants and algae?
Sporophyte
How does a sporophyte make haploid spores?
Meiosis
Each spore grows by mitosis into a haploid organism called a
Gametophyte
How does a gametophyte make haploid gametes
Mitosis
In most fungi and some protists the only diploid stage is
The single-celled zygote
Is there amulticellular diploid stage in fungi and protists?
no
How does the zygote of fungi and protists produce haploid cells?
Meiosis
True or false: In fungi and protists each haploid cell grows by mitosis into a haploid multicellular organism
True
In fungi and protists how do haploid adults produce gametes?
Mitosis
True or false: depending on the type of life cycle either haploid or diploid cells can divide by mitosis
True
True or false: only diploid cells can undergo meiosis
True
True or false: in all three life cycles chromosome halving and doubling do not contribute to genetic variation in offspring
False.
In comparing the typical life cycles of plants and animals a stage found in plants but not in animals is a
Multicellular haploid
True or false: Meiosis is not preceded by the replication of chromosomes
False
What occurs during Meiosis 1 interphase?
- Chromosomes are replicated to form sister chromatids
- Sister chromatids are genetically identical and joined at the centromere
What occurs during Meiosis 1 interphase?
- Chromosomes are replicated to form sister chromatids
- Sister chromatids are genetically identical and joined at the centromere
What are the two sets of cell divisions in which meiosis takes place?
Meiosis I and Meiosis II
What happens in the first cell division (meiosis I)
homologous chromosomes separate and results in two haploid daughter cells with replicated chromosomes
What happens in the second cell division (meiosis II)
Sister chromatids separate resulting in four haploid daughter cells with unreplicated chromosomes
What is the overall result of Meiosis I and II
four daughter cells rather than the two daughter cells in mitosis
True or false: In meiosis each daughter cell has only half as many chromosomes as the parent cell?
True
What are the main phases of Meiosis I?
Interphase Prophase I Metaphase I Anaphase I Telophase I
What happens in interphase during Meiosis I?
Single centrosome replicates forming two centrosomes and chromosomes duplicate
What happens in prophase I?
In synapsis, homologous chromosomes loosely pair up, aligned gene by gene.
- Crossing over occurs
- Each pair of chromosomes forms a tetrad
Define tetrad
a group of four chromatids
Define chiasmata
X shaped regions where crossing over occurred
What happens in Metaphase I
Tetrads line up at the metaphase plate
Independent assortment occurs
What happens in Anaphase I
Sister chromatids remain attached and pairs of homologous chromosomes split up
What happens in Anaphase I
Sister chromatids remain attached and pairs of homologous chromosomes split up
What happensin telophase I?
Cleavage furrow forms, two haploid cells form, chromosomes are still doubled
Does chromosome replication occur between meiosis I and II?
NO
Are sister chromatids of each chromosome genetically identical? Why/Why not?
No
Crossing over
What happens during prophase II?
Spindle apparatus forms
What happens during Metaphase II?
Sister chromatids are arranged at the metaphase plate
What is the name of the cleavage furrow in plant cells?
Cell Plate
What happens during Anaphase II?
Sister chromatids separate
What happens in Telophase II?
Four haploid daughter cells result containing single chromosomes
True or false: each daughter cell formed in Meiosis II are genetically identical to others and the parent cell
False. They are genetically different
Is Meiosis I or Meiosis II most similar to Mitosis?
Mitosis II
Does Mitosis or Meiosis conserve the number of chromosome sets producing cells that are genetically identical to the parent cell?
Mitosis
Does Mitosis or Meiosis reduce the number of chromosomes sets from diploid to haploid producing cells that differ genetically from each other and the parent cell
Meiosis
True or false: The mechanism for separating sister chromatids is virtually identical in meiosis II and mitosis
True
What three events are used to distinguish meiosis from mitosis?
- Synapsis and crossing over
- Tetrads on the metaphase plate
- Separation of homologues
What is the original source of genetic diversity?
Mutations (changes in an organism’s DNA)
What produces genetic variation?
Reshuffling of different versions of genes during sexual reproduction
What produces genetic variation?
Reshuffling of different versions of genes during sexual reproduction
True or false: The behavior of chromosomes during meiosis and fertilization is responsible for most of the variation that arises in each generation
True
What three mechanisms contribute to genetic variation
- Independent assortment of chromosomes
- Crossing over
- Random Fertilization
What is independent assortment?
Each pair of chromosomes sorts maternal and paternal homologues into daughter cells independently of the other pairs
When do homologous pairs of chromosomes orient randomly?
Metaphase I of meiosis
What is the number of combinations possible when chromosomes assort independently into gametes?
2^n
where n is the haploid number
ex// humans (n=23) so 2^23 possible combinations of chromosomes
What does crossing over produce?
recombinant chromosomes which combine genes inherited from each parent
When does crossing over begin?
very early in prophase I as homologues pair up gene by gene
In crossing over, homologous portions of two non sister chromatids
trade places
How does randum fertilization add to genetic variation?
Any sperm can fuse with any ovum (unfertilized egg)
The fusion of two gametes produces a zygote with how many diploid combinations?
70 trillion
The fusion of two gametes produces a zygote with how many diploid combinations?
70 trillion
The chromosome theory of inheritance states:
- Mendelian genes have specific loci (positions on chromosomes)
- It is the chromosomes that undergo segregation and independent assortment
What is the law of segregation?
The two alleles for each gene separate during gamete formation
What is the Law of independent assortment?
Alleles of genes on nonhomologous chromosomes assort independently during gamete production
What is an organism’s sex?
An inherited phenotypic character determined by the presence or absence of chromosomes
What is SRY
Sex- determining region of Y, gene on the Y chromosome responsible for the development of the testes.
Do x chromosomes have genes for many characters unrelated to sex?
Yes
A gene that is located on either sex chromosome is called a
sex-linked gene
Genes on the Y chromosome are called
Y-linked genes
Genes on the X chromosome are called ____ and follow specific patterns of inheritance
X-linked genes
For a recessive X-linked trait to be expressed
A female needs two copies of the allele (homozygous)
A male needs only one copy of the allele (hemizygous)
Xlinked recessive disorders are much more common in
males
What type of disorders are caused by recessive alleles on the X chromosome?
Color blindness, Duchenne muscular dystrophy, hemophilia
What is a linkage map?
A genetic map of a chromosome based on recombination frequencies.
Distances between genes can be expressed as
map units (1 map unit= 1% recombination frequency)
True or false: The farther apart 2 genes are the higher the probability a crossover will occur between them and the higher the recombination frequency
TRUE
What is the max recombination frequency genes on the same chromosome can have?
50%
When genes are far apart on the same chromosome they are
Physically linked, genetically unlinked, and behave as if found on different chromosomes
Linkage maps can portray the order of genes along a chromosome but
does not accurately portray the precise location of these genes
Linkage maps can portray the order of genes along a chromosome but
does not accurately portray the precise location of these genes
Chromosomal banding helps geneticist develop
Cytogenic maps
What is a cytogenic map?
Indicates the positions of genes with respect to chromosomal features
Large-scale chromosomal alterations often lead to
Spontaneous abortions (miscarriages) or cause a variety of developmental disorders
What is nondisjunction
Pairs of homologous chromosome do not separate normally during meiosis
What is the result of nondisjunction?
One gamete receives two of the same type of chromosome and another gamete receives no copy
Define aneuploidy
Result of fertilization of gametes in which nondisjunction occurred, offspring have an abnormal # of a particular chromosome
What is a trisomic zygote?
Three copies of a particular chromosome
What is a monosomic zygote?
Has only one copy of a particular chromosome
Define polyploidy
An organism has more than 2 complete sets of chromosomes
What are the 4 types of changes in chromosome structure?
Deletion
Duplication
Inversion
Translocation
What is deletion?
A chromosomal unit is removed
What is Duplication
it repeats a segment
What is inversion
Reverses a segment within a chromosome
What is a translocation
Moves a segment from one chromosome to a nonhomologous chromosome
What disorders are due to chromosomal alterations?
Down syndrome Kinefelter syndrome Monosomy X Cri du Chat Chronic melogenous leukemia
What causes down syndrome and how many children does it effect?
- Is a trisomy 21 (three copies of chromosome 21)
- It effects one out of every 700 children born in the US
- Frequency of down syndrome increases with the age of the mother
Nondisjunction of sex chromosomes produces thes aneuploid conditions
Klinefelter syndrome and Monosomy X
What is Klinefelter syndrome caused by?
The result of an extra chromosome in a male prducing an XXY individual
What is Monosomy X?
Also called Turner Syndrome, produces sterile X0 Females, only known viable monosomy in humans
What is Monosomy X?
Also called Turner Syndrome, produces sterile X0 Females, only known viable monosomy in humans
What is Cri du chat?
- “Cry of the cat”
- Caused by deletion in chromosome 5
- A child is mentally rettarded and has catlike cry, dies early
What causes Chronic Myelogeneous leukemia?
Translocations of chromosomes
The fusion of two gametes produces a zygote with how many diploid combinations?
70 trillion
What causes Chronic Myelogeneous leukemia?
Translocations of chromosomes
How can we tell the genotype of an individual with the dominant phenotype?
The testcross
How did Mendel indentify his second law of inheritance?
Following two characters at the same time
Crossing two true-breeding parents differing in two characters produces
Dihybrids
What is a dihybrid cross?
Determines whether two characters are transmitted to offspring as a package or independently
What is the phenotypic ratio of a dihybrid cross?
9:3:3:1
True or false: Mendel’s laws of segregation and independent assortment do not reflect the rules of probability
False
Describe the multiplication rule
The probability that two or more independent events will occur together is the product of their individual probabilities
Describe the rule of addition
The probability that any one of 2 or more excllusive events will occur is calculated by adding together their individual probabilities
Inheritance of characters by a single gene may deviate from simple mendelian patterns when:
- Alleles are not completely dominant or recessive
- A gene has more than two alleles
- A gene produces multiple phenotypes
What occurs when phenotypes of the herozygote and dominant homozygote are identical?
Complete dominance
What is incomplete dominance
The phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties
What is codominance?
Two dominant alleles affect the phenotype in separate distinguishable ways
Is hypercholesterolemia completely dominant?
No. It is incompletely dominant
Is hypercholesterolemia completely dominant?
No. It is incompletely dominant
Does a dominant allele subdue a recessive allele?
No
Do alleles interact?
No
What are alleles?
Variations in a gene’s nucleotide sequence
True or false: The observed dominant recessive relationship of alleles depends on the level we examine the phenotype
True
What is Tay-Sachs disease
Fatal
Dysfuntional enzyme causes an accumulation of lipids in the brain
True or false: Dominant alleles are more common in populations than recessive alleles
False.
True or false: Most genes do not exist in populations in more than two allelic forms
False
What blood type is a universal donor?
O
What blood type is a universal acceptor?
AB
The immune system produces antibodies which may cause ___ when blood cells of a different type enter the body
Clotting
What determines the positive or negative in regards to blood type
The Rhesus factor (RhD antigen) on the surface of red blood cells
A person who does have the RhD antigen is
Positive
A person who does not have the RhD antigen is
Negative
Describe complete dominance of one allele
Heterozygous phenotype same as that of homozygous dominant
Describe incomplete dominance of either allele
Heterozygous phenotype intermediate between the two homozygous phenotypes
Describe codominance
Both phenotypes are expressed in heterozygotes
Describe multiple alleles
In the whole population some genes have more than two alleles
Describe Pleiotropy
One gene is able to affect multiple phenotypic characters
Describe Epistasis
The phenotypic expression of one gene affects that of another
Describe Polygenic Influence
A single phenotypic character is affected by two or more genes
If two parents have a trait and an offspring does not, the train can not be a
Recessive trait
If two parents lack a trait but an offspring has it, the trait must be
Recessive
If two parents lack a trait but an offspring has it, the trait must be
Recessive
Describe Albinism. Is it a dominant or recessive disorder?
Lack of pigment in skin, hair and eyes
Recessive
Describe cystic fibrosis. Is it a dominant or recessive disorder?
Excess mucus in lungs, increased susceptibility to infections
Results in defective or absent chloride transport channels
Recessive
Describe Sickle Cell Disease (homozygous)
Sickled red blood cells caused by substitution of a single amino acid in the hemoglobin protein
Recessive
Describe Achondroplasia
Dwarfism
Dominant Disorder
Describe HUntington’s disease
Mental deterioration and uncontrollable movements
Dominant disorder
Do recessively inherited disorders show up only in individuals homozygous for the allele?
Yes
What are carriers?
Heterozygous individuals who carry the recessive allele but are pheotypically normal
Can mutant alleles create a benefit? Give an example
Yes
Sickle cell kids are resistant to malaria
What are the consequences of inbreeding?
Increased probability of the appearance of a genetic disease
What is a multifactorial disorder?
Diseases with genetic and environment components
What are the main examples of Multifactorial disorders?
Heart disease Cance Diabetes Alcoholism Mental Illnesses
What are the two types of fetal testing?
Amniocentesis and Chorionic villus sampling
What is amniocentesis
Liquid that bathes fetus is removed and tested
What is Chorionic Villus Sampling
CVS, sample of placenta is removed and tested.
