Harold Washington Bio 121 Test 4

Front 1

somatic cells

Back 1

(non-reproductive cells) have two sets of chromosomes. Diploid or 2n; Humans have 46 chromosomes in their somatic cells

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chromatin

Back 2

Eukaryotic chromosomes consist of this; a complex of DNA and protein that condenses during cell division

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gametes

Back 3

reproductive cells: sperm and eggs; have half as many chromosomes as somatic cells. Haploid or n. During fertilization, sperm and eggs unite, passing on genes of both parents to their offspring

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sister chromatids

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Each duplicated chromosome has two of these (joined copies of the original chromosome), attached along their lengths by protein molecules (cohesins)

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centromere

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the narrow “waist” of the duplicated chromosome, where the two chromatids are most closely attached

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mitosis

Back 6

a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

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cytokinesis

Back 7

the division of the cytoplasm

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phases of the cell cycle

Back 8

The cell cycle consists of the Mitotic (M) phase (mitosis and cytokinesis) and Interphase (cell growth and copying of chromosomes in preparation for cell division)

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Cell Cycle: interphase

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90% of the cell cycle:G1 phase (“first gap”) First Growth; S phase (“synthesis”); G2 phase (“second gap”) second growth. The cell grows during all three phases, but chromosomes are duplicated only during the S phase

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centrosome

Back 10

In animal cells, assembly of spindle microtubules begins in the _______; replicates during interphase, forming two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase

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Cell cycle: Interphase G1

Back 11

A growth period, which occurs immediately after mitosis

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Cell cycle: Interphase S

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period when DNA is replicated (chromosome replication occurs). Each replicated chromosome consists of 2 sister chromatids

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Cell cycle: Interphase G2

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A growth period, which prepares the cell for the next mitotic division. Centrioles replicate in this stage, in animal cells; Nucleus and nucleolus are still in tact.

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Cell cycle: Mitosis prophase

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The nucleolus disappears. The replicated chromosomes coil tightly to appear as rod-shaped structures. Each duplicated chromosome appears as 2 identical sister chromatids joined at their centromeres. The mitotic spindle begins to form. The centrosomes move away from each other.

Front 15

Cell cycle: Mitosis prometaphase

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The nuclear envelope fragments. The chromosomes become even more condensed. Each of the 2 chromatids of each chromosome now has a kinetochore. Some of the microtubules attach to the kinetochores which jerk the chromosomes back and forth

Front 16

Cell cycle: Mitosis metaphase

Back 16

The centrosomes are now at opposite poles of the cell. The chromosomes have all arrived at the metaphase plate.

Front 17

Cell cycle: Mitosis anaphase

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The centromeres and cohesin proteins of the sister chromatids separate. The shortening of the spindle fibers pulls the sister chromatids toward opposite poles. Once sister chromatids separate and begin moving to opposite poles, they are called daughter chromosomes

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Cell cycle: Mitosis telophase

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Two daughter nuclei form in the cell. Nuclear envelopes arise. Nucleoli reappears. The chromosomes start to uncoil.

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Cell cycle: Mitosis cytokinesis

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Cytoplasmic division begins prior to the end of telophase. A cleavage furrow forms, which constricts until the parent cell divides to produce 2 daughter cells.

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kinetochore

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A structure made up of proteins that have assembled on specific sections of DNA at each centromere. During prometaphase, some spindle microtubules attach to these and begin to move the chromosomes

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metaphase plate

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At metaphase: an imaginary line, between the spindle’s 2 poles, where the centromeres of all duplicated chromosomes line up

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separase

Back 22

In anaphase the cohesins are cleaved by this enzyme; when all the kinetochores are attached to spindle microtubules is ___ activated and anaphase begins

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cohesins

Back 23

The protein molecules that attach sister chromatids together along their length

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Cytokinesis in plants vs animals

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In plant cells, a cell plate forms during cytokinesis; in animal cells, a cleavage furrow forms between; In animal cells, cytokinesis occurs by a process known as cleavage, forming a cleavage furrow

Front 25

protein kinases and cyclin-dependent kinases (Cdks)

Back 25

Two types of regulatory proteins are involved in cell cycle control: protein kinases and cyclins; Many of the kinases that drive the cell cycle are actually present at a constant concentration in the cell but are often in an inactive form. To be active, such a kinase must be attached to a cyclin. The activity of a Cdk rises and falls with changes in concentration of its cyclin partner

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cyclin

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A protein that gets its name from its cyclically fluctuating concentration in the cell

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MPF

Back 27

a cyclin-Cdk complex that triggers a cell’s passage past the Interphase G2 checkpoint into the M phase (triggers the events of mitosis)

Front 28

growth factors and PDGF

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an external factor that influences cell division; released by certain cells and stimulate other cells to divide; platelet-derived growth factor (PDGF) is made by blood cell fragments called platelets

Front 29

density-dependent inhibition (might not need this one)

Back 29

a phenomenon in which crowded cells stop dividing

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anchorage-dependent cells

Back 30

to divide, these cells must be attached to a substratum

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some reasons why cancer cells grow out of control

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Density-dependent inhibition and anchorage dependence check the growth of cells at an optimal density; Cancer cells exhibit neither type of regulation of their division; Cancer cells may not need growth factors to grow and divide; some make their own growth factor; some convey a growth factor’s signal without the presence of the growth factor; some have an abnormal cell cycle control system

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sexual reproduction

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2 parents give rise to offspring that have unique combinations of genes inherited from the 2 parents

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germ cells

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the only cells of the human body not produced by mitosis are the gametes, which develop from specialized cells called germ cells in the ovaries or testes

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zygote

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a fertilized egg; diploid because it contains 2 haploid sets of chromosomes, bearing genes representing the maternal and paternal family

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diploid

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any cell with 2 chromosome sets; (for humans, the ___ number is 46 (2n=46)

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haploid

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any cell with only a single set of chromosomes; for humans, the ___ number is 23 (n=23). The set of 23 consists of the 22 autosomes plus a single sex chromosome

Front 37

asexual reproduction

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a single individual is the sole parent and passes copies of all its genes to its offspring without the fusion of gametes. Progeny is not genetically diverse

Front 38

Chromosomes

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are in pairs, one from each parent

Front 39

homologous chromosomes

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the 2 chromosomes of a pair that have same length, centromere position, and staining pattern

Front 40

female vs male

Back 40

The set of 23 chromosomes in gametes consists of the 22 autosomes plus a single sex chromosome. An unfertilized egg contains an X chromosome, but a sperm may contain an X or a Y. Female = XX

Front 41

meiosis and chromosomes

Back 41

as a result of meiosis, each human sperm and egg is haploid (n=23). Fertilization restores the diploid condition by combining 2 haploid sets of chromosomes

Front 42

Meiosis

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in sexually reproducing organisms, gamete formation involves this type of cell division. It reduces the number of sets of chromosomes from 2 to one in the gametes, counterbalancing the doubling that occurs in fertilization

Front 43

Meiosis I goal

Back 43

Separates homologous chromosomes

Front 44

Meiosis II goal

Back 44

Separates sister chromatids

Front 45

Meiosis I: Prophase I

Back 45

During the beginning of this phase, each chromosome pairs with its homolog, aligned gene by gene and crossing over occurs. During the end of this phase, microtubules from each pole will attach to the 2 kinetochores and will move towards the metaphase plate

Front 46

Meiosis I: Metaphase I

Back 46

Pairs of homologous chromosomes are now arranged at the metaphase plate. Both chromatids are attached to kinetochore microtubules from each pole

Front 47

Meiosis I: Anaphase I

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Sister chromatid cohesins break apart and allow homologs to separate. Homologs move towards opposite poles

Front 48

Meiosis I: Telophase I and Cytokinesis

Back 48

Each half of the cell has a complete haploid set of duplicated chromosomes. Each chromosome is composed of 2 sister chromatids; one or both chromatids include regions of nonsister chromatid DNA.

Front 49

Meiosis II: Prophase II

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(2 daughter cells at this point). a spindle apparatus forms. chromosomes move towards the metaphase II plate.

Front 50

Meiosis II: Metaphase II

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The chromosomes are positioned at the metaphase plate as in mitosis. because of crossing over in meiosis I, the 2 sister chromatids of each chromosome are NOT genetically identical. The kinetochores of sister chromatids are attached to microtubules extending from opposite poles.

Front 51

Meiosis II: Anaphase II

Back 51

breakdown of proteins holding sister chromatids together allows the chromatids to separate. chromatids move towards opposite poles as individual chromosomes

Front 52

Meiosis II: Telophase Ii and Cytokinesis

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nuclei form, the chromosomes begin decondensing and cytokinesis occurs. The division of one parent cell produces 4 daughter cells, each with a haploid set of (unduplicated) chromosomes. The 4 daughter cells are genetically distinct from one another and from the parent cell.

Front 53

crossing over

Back 53

After interphase the sister chromatids are held together by proteins called cohesins. The nonsister chromatids are broken at precisely corresponding positions. DNA breaks are repaired, joining DNA from one non-sister chromatid to the corresponding segment of another. also known as recombination

Front 54

independent assortment

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Because each pair of homologous chromosomes is positioned independently of the other pairs at metaphase I, the first meiotic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair

Front 55

When does genetic variation occur?

Back 55

Crossing over, fertilization, and in independent assortment of chromosomes

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Gregory Mendel

Back 56

discovered the basic principles of heredity. (1) alternative versions of genes account for variations in inherited characters. (2) for each character, organism inherits 2 copies of a gene, 1 from each parent. (3) if the 2 alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance; recessive allele, has no effect on the appearance. (4) the 2 alleles for a heritable char segregate during gamete formation and end up in different gametes.

Front 57

true breeding plants

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varieties of plants that, over many generations of self-pollination, have produced only the same variety as the parent plant

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character

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a heritable feature that varies among individuals, such as flower color

Front 59

traits

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each variant for a character, such as purple or white color for flowers

Front 60

P generation

Back 60

the true-breeding parents in Mendel’s experiments

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F1 generation (and what is the ratio)

Back 61

the offspring of the P generation (first filial generation). This generation is considered a hybrid. All plants showed the dominant trait

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F2 generation (and what is the ratio)

Back 62

the offspring of F1 hybrids; ratio is approximately 3:1 dominant to recessive

Front 63

Punnett square (Pp + pp)

Back 63

a diagrammatic device for predicting the allele composition of offspring from a cross between individuals of known genetic makeup

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allele

Back 64

the alternative versions of a gene

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phenotype

Back 65

observable traits of an organism

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genotype

Back 66

genetic makeup of an organism

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homozygous

Back 67

An organism that has a pair of identical alleles for a character

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heterozygous

Back 68

An organism that has 2 different alleles for a gene

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Incomplete dominance

Back 69

For some genes, neither allele is completely dominantt and the F1 hybrids have a phenotype somewhere between those of the 2 parental varieties

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complete dominance

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A kind of dominance wherein the dominant allele completely masks the effect of the recessive allele in heterozygous condition. (When phenotypes of the heterozygote and dominant homozygote are identical; The F1 offspring always look like one of the 2 parental varieties)

Front 71

codominance

Back 71

the 2 alleles each affect the phenotype in separate, distinguishable ways. A condition in which the alleles of a gene pair in a heterozygote are fully expressed thereby resulting in offspring with a phenotype that is neither dominant nor recessive.

Front 72

epistasis

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the phenotypic expression of a gene at one locus alters that of a gene at a second locus

Front 73

E gene

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Labrador example: the dominant allele; results in the deposition of either black or brown pigment, depending on the genotype at the first locus. If the lab is homozygous recessive for the 2nd locus (ee), then the coat is yellow, regardless of the genotype at the black/brown locus

Front 74

recessive inherited disorders

Back 74

Many genetic disorders are inherited in a recessive manner; only in individuals homozygous for the allele; a gene codes for a protein of specific function. An allele that codes for a genetic disorder either codes for a nonfunctional protein or no protein at all; albinism

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carrier

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Carriers are heterozygous individuals who carry the recessive allele but are phenotypically normal; most individuals with recessive disorders are born to carrier parents; AA (not a carrier); Aa (carrier)

Front 76

dominant disorders

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the presence of even one allele is sufficient to cause the disease; Dominant alleles that cause a lethal disease are rare and arise by mutation; Achondroplasia is a form of dwarfism caused by a rare dominant allele.

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cystic fibrosis

Back 77

The _____ allele results in defective or absent chloride transport channels in plasma membranes leading to a buildup of chloride ions outside the cellSymptoms include mucus buildup in some internal organs and abnormal absorption of nutrients in the small intestine

Front 78

Sickle cell disease

Back 78

The disease is caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells. In homozygous individuals, all hemoglobin is abnormal

Front 79

Morgan (genes are on chromosomes)

Back 79

Morgan mated male flies with white eyes (mutant) with female flies with red eyes (wild type): The F1 generation all had red eyes; The F2 generation showed a 3:1 red to white eye ratio, but only males had white eyes

Front 80

Fly experiment

Back 80

Morgan’s discovery of a trait that correlated with the sex of flies was key to the development of the chromosome theory of inheritance

Front 81

X and Y chromosomes in determining sex

Back 81

In humans and other mammals, there are two varieties of sex chromosomes: a larger X chromosome and a smaller Y chromosome; A person with XX develops as a female, while a male develops from a zygote with XY; Only the ends of the Y chromosome have regions that are homologous with corresponding regions of the X chromosome

Front 82

sex-linked gene

Back 82

A gene that is located on either sex chromosome is called a sex-linked gene; Morgan’s discovery of a trait that correlated with the sex of flies was key to the development of the chromosome theory of inheritance; In humans and some other animals, there is a chromosomal basis of sex determination

Front 83

sex-linked diseases (x-link and y-link diseases)

Back 83

Fathers pass X-linked alleles only to their daughters and none of their sons, while mothers pass X-linked alleles to both daughters and sons. X-linked recessive disorders are much more common in males than in females; 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)

Front 84

color blindness (x link)

Back 84

This is almost always inherited as an X-linked trait. A color-blind daugter may be born to a color-blind father whose mate is a carrier.

Front 85

SRY

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A gene on the Y chromosome called SRY (sex-determining region on the Y) is responsible for development of the testes in an embryo. In the absence of SRY (absence of Y chromosome) the gonads develop into ovaries

Front 86

males give x to daughters; females give X to daughters?

Back 86

Fathers pass X-linked alleles only to their daughters and none of their sons, while mothers pass X-linked alleles to both daughters and sons

Front 87

colorblind activity in book (# of kids who are colorblind if colorblind male and carrier is female)

Back 87

desktop

Front 88

x-inactivation; mosaicism, Barr body

Back 88

In mammalian females, one of the two X chromosomes in each cell, is randomly inactivated during embryonic development. The inactive X condenses into a Barr body. This inactivation occurs randomly and independently in each cell. If a female is heterozygous for a particular gene located on the X chromosome, she will be a mosaic for that character

Front 89

linked genes (if gene is on 2 chromosomes, parental form and recombinant). (if gene is on same chromosome, only parental depending on closeness)

Back 89

Offspring with nonparental phenotypes (new combinations of traits) are called recombinant types, or recombinants;

Front 90

crossing over as it relates to linked genes

Back 90

Morgan discovered that genes can be linked, but the linkage was incomplete, because some recombinant phenotypes were observed; He proposed that some process must occasionally break the physical connection between genes on the same chromosome; That mechanism was the crossing over of homologous chromosomes

Front 91

map unit

Back 91

Distances between genes; one _____, or centimorgan, represents a 1% recombination frequency

Front 92

genetic map

Back 92

an ordered list of the genetic loci along a particular chromosome. Sturtevant predicted that the farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency

Front 93

alterations of chromosome number or structure

Back 93

___ cause some genetic disorders; Large-scale ___in humans and other mammals often lead to spontaneous abortions (miscarriages) or cause a variety of developmental disorders

Front 94

polyploidy

Back 94

a condition in which an organism has more than two complete sets of chromosomes; Triploidy (3n) is three sets of chromosomes; Tetraploidy (4n) is four sets of chromosomes

Front 95

aneuploidy

Back 95

results from the fertilization of gametes in which nondisjunction occurred; Offspring with this condition have an abnormal number of a particular chromosome

Front 96

nondisjunction

Back 96

pairs of homologous chromosomes or sister chromatids do not separate normally during meiosis; As a result, one gamete receives two of the same type of chromosome, and another gamete receives no copy

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monosomic

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zygote has only one copy of a particular chromosome

Front 98

trisomic

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zygote has three copies of a particular chromosome

Front 99

Down syndrome

Back 99

an aneuploid condition that results from three copies of chromosome 21

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duplication

Back 100

Breakage of a chromosome can lead to four types of changes in chromosome structure: ___this___ repeats a segment

Front 101

deletion

Back 101

Breakage of a chromosome can lead to four types of changes in chromosome structure: ___this___ removes a chromosomal segment

Front 102

inversion

Back 102

Breakage of a chromosome can lead to four types of changes in chromosome structure: ___this___ reverses orientation of a segment within a chromosome

Front 103

translocation

Back 103

Breakage of a chromosome can lead to four types of changes in chromosome structure: ___this___ moves a segment from one chromosome to another

Front 104

XXX females

Back 104

Nondisjunction of sex chromosomes produces a variety of aneuploid conditions; XXX females are healthy, with no unusual physical features

Front 105

XXY individuals

Back 105

Klinefelter syndrome is the result of an extra chromosome in a male, producing. Males have abnormally small testis and are sterile, have breast enlargement and feminine characteristics

Front 106

X0 females

Back 106

Monosomy X, called Turner syndrome, produces X0 females, who are sterile; it is the only known viable monosomy in humans

Front 107

inheritance of mitochondrial dna and organelles

Back 107

Extranuclear genes (or cytoplasmic genes) are found in organelles in the cytoplasm; Mitochondria, chloroplasts, and other plant plastids carry small circular DNA molecules; Extranuclear genes are inherited maternally because the zygote’s cytoplasm comes from the egg