BIO 211 Exam 3

Place the events that control the progression of cells through the G1/S checkpoint of the cell cycle in order.

1. cyclins D and E bind CDK proteins 2. Cyclin-CDK complexes phosphorylate RB proteins 3. Inactivated RB releases active E2F protein 4. E2F transcribes genes required for DNA replication.

sex determination in fruit flies

1.0 females .5 males

missense mutation

A base-pair substitution that results in a codon that codes for a different amino acid.

double fertlization

A mechanism of fertilization in angiosperms, in which two sperm cells unite with two cells in the embryo sac to form the zygote and endosperm.

nonsense mutation

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

in-frame deletions

Deletion of some multiple of three nucleotides, which does not alter the reading frame of the gene.

DNA damage can occur as a result of exposure to chemicals or ultraviolet radiation. what happens during nucleotide excision repair of damaged DNA?

Enzymes open the DNA strand, remove a segment of DNA from the strand that contains the damage, and resynthesizes the correct DNA sequence

XX-XY

Females are XX Males are XY

ZZ-ZW

Females are ZW Males are ZZ

haploinsufficient

For a particular gene, one functioning copy is not enough for a wildtype phenotype.

in-frame insertions

Insertion of some multiple of three nucleotides, which does not alter the reading frame of the gene

Substitution, Deletion, Insertion

Know the differences

Female gametogenesis (oogenesis)

Oogonia (2n) > Oogonium (2n) > primary oocytes (2n) > secondary oocyte (1n) and first polar body > Ovum (1n) and second polar body

Suppose Alia recently learned that she inherited a mutant RB1 allele from her mother, who had retinoblastoma. RB1 is a tumor suppressor gene that is related to retinoblastoma. Why would Alia be at higher risk for getting retinoblastoma at an earlier age than her sister, Francine, who inherited a normal RB1 allele from their mother?

Someone with one mutant allele in a tumor suppressor gene only requires a mutation in the one remaining normal allele for tumors to form.

klinefilter syndrome

The most common genitic order in males in which they have an extra 47 chrosome (XXY) Symptoms include haveing small, firm testes, gynecomastia, abnormally long legs, minimal body & facial hair, & are infertile.

why are these effects. less noticeable for multisomies and monosomes of the X chromosomes in humans

X inactivation only allows one X chromosome to be expressed in any given cell

turner syndrome

XO

Select the true statements regarding the roles of sex chromosomes in human development

XXY males are often fertile XO females are often sterile an individual missing the SRY region of the Y chromosome will be phenotypically female

select the definition of polyploidy

a chromosomal complement with at least three complete sets of homologous chromosomes

Translocations

a chromosomal translocation involves movement of genetic material between non homologous chromosomes

Deletions

a chromosome deletion is the loss of a chromosome segment

duplications

a chromosome duplication is a mutation in which part

Inversions

a chromosome inversion is when a segment of the chromosome is inverted, or turned 180 degrees

non-reciprocal translocation

a genetic material moves from one chromosome to another without any reciprocal exchange

n=3

a genome composed of three unique chromosomes

which of the mutations described have the potential to cause cancer

a loss-of-function mutation in a tumor suppressor gene a gain-of-function mutation in a porto-oncogene

Select the statements that accurately describe different ways that translocations could lead to cancer?

a translocation disrupts the sequence of a gene for a tumor-suppressor protein. the resulting protein cannot function properly. A new sequence is added to a porto-oncogene. the modified gene now produces a new protein that increases the rate of cell division. A gene for a protein that is involved in a mitotic checkpoint is placed next to the regulatory sequence of a different gene. the gene is now expressed at inappropriate times.

reciprocal translocations

a two-way exchange of segments between the chromosomes

Insertions and Deletions

additions or losses of nucleotide pairs in a gene

Base substitutions

alter a single nucleotide in the DNA

chromosome rearrangments

alter the structure of the chromosome

Barr body

an inactive X chromosome

mutation

an inherited change in genetic information

somatic mutations

arise in cells that do not produce gametes

germ-line mutations

arise in cells that produce gametes

Dosage compensation

balances the dose of X chromosome gene expression in females and males females have barr bodies

sex

biological differences between males and females

Cancers may either be inherited or they may be induced by environmental factors such as carcinogens and radiation. select the statement that explains how diverse factors such as hereditary events and environmental agents can both cause cancer

both hereditary and environmental factors deregulate cell cycle checkpoint response

Monoecious

both male and female reproductive structures

hermaphroditism

both sexes present in the same organism

How do viruses contribute to cancer?

by driving over expression of a cellular proto-oncogene by inactivating tumor suppressor genes

Aneuploidy

change in the # of individual chromosomes ex. 2n-1 and 2n+1 can rise from loss of chromosome during mitosis or meiosis, a robertsonian translocation, nondisjunction

Which type of DNA mutation results in a change in the reading frame of an mRNA?

deletion of a single nucleotide

position effect

dependence of the expression of a gene on the gene's location in the genome

pericentric inversions

do include the centromere

paracentric inversions

do not include the centromere

in c.elegans, the level of expression of genes on both X chromosomes of females is reduced by half

dosage compensation

Ohno's hypothesis

duplicated chromosomes may play a role in the evolution of new genes

unbalanced gene dosage

duplications can have sever consequences when balance of gene products thrown off to cell function

4 types of chromosome rearrangements

duplications, deletions, inversions, translocations

The first cloned cat, CarbonCopy (CC), was tabby, while the cat she was cloned from, Rainbow, was calico. The surrogate mother was a tabby. Select the explanation that best explains why CC would never have been identical in pattern to Rainbow.

during embryogenesis, one X chromosome is randomly inactivated in each cell lineage

pseudodominance

expression of a normally recessive allele owing to a deletion on the homologous chromosome

Which statements describe Y-linked traits?

female offspring cannot inherit the trait the phenotype is solely expressed in males

XX-XO

females are XX Males are XO

Identical, or monozygotic, twins develop from a single egg fertilized by a single sperm. Monozygotic twins are genetically identical because they originate from a single zygote that split into two. Caroline Loat and her colleagues examined nine measures of social, behavioral, and cognitive ability in 1000 pairs of both male and female identical twins. Their study found that pairs of male twins tended to be more alike in their prosocial behavior, peer problems, and verbal ability scores than pairs of female twins. Which statement explains this observation?

females are mosaic for the expression of heterozygous X-linked loci, because females undergo random X-inactivation

in the XX-XO mechanism of sex determination, which of the statements is true?

females have two X chromosomes (XX) and males have one X chromosome (XO)

gender

gender role gender identity

Chromosome duplications and deletions frequently result in abnormal phenotypes or inviable gametes. Which factor is a major contributor to this phenomenon?

gene dosage is modified

genie sex determination

genotypes at specific loci determine the sex of the individual plants, fungi, protozoans, fishes

Shugoshin

holds sister chromatids during anaphase I in meiosis

cohesin

holds sister chromatids together in mitosis

Both genes and environmental factors contribute to cancer. The table shows that prostate cancer is 30 times more common among Caucasians from Utah as among Chinese from Shanghai. Briefly outline how to determine if these differences in the incidence of prostate cancer are due to differences in the genetic makeup of the two populations or to differences in their environments.

if the differences are due to genetic makeup only, then people who migrated from Utah or Shanghai to elsewhere would have a similar cancer rate as people who stayed inUtah or Shangai If the differences are due to the environment only, then people who migrated from Utah or Shanghai would have rates of cancer determined by their location and not by their place of origin

Polyploidy

increase in the # of chromosome sets ex. 4N, 2N Autoplolyploidy v. allopolyploidy

AB x CDEFG > ABx CFEDG

inversion

see which examples are induced mutation

ionizing radiation causes chromosomal fragmentation nitrous acid causes the deamination of adenine to hypoxanthine

A fruit fly only has one sex chromosome (XO) and two sets of autosomes would have which sexual phenotype

male

Ovary

megasporocytes > four haploid megaspores > divides three time to produce eight haploid nuclei

Chi-du-chat syndrome

mental retardation, abnormal development of glottis and larynx

Stamen

microsporocytes > 4 haploid microspres > pollen grain > pollen tube with two haploid sperm cells

a chromosomal translocation refers to

movement of a chromosome segment to a non homologous chromosome

frameshift mutation

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

Failure to separate for homologous chromosomes or sister chromatids is referred to as

nondisjuction

trisomic

one extra copy of a specific chromosome

polyploidy

one or more complete sets of chromosomes are added

Dioecious

organism is either male or female ex. humans

ABxCDEFG > ABx CFEDG

paracentric

ABxCDEFG > ABCx BEFG

pericentric

transition

purine replaced by purine or pyrimidine with a pyrimidine

transversion

purine replaced by pyrimidine or pyrimidine replaced by purine

Colorblindness is a sex-linked recessive trait. a female is color blind in one eye, but not both. select the explanation, is it possible for a male to have different color-blindness phenotypes in each eye?

random X-chromosome inactivation yes, in an XXY male with a different active X in each eye

expanding nucleotide repeats

repeated sequence of a set of nucleotides in which the number of copies of the sequence increases

environmental sex determination

sex is determined fully or in part by environmental factors

Somatic, gametic, both

somatic mutation: -the mutation occurs in any cell except a germ cell, and thus the mutation does not affect the progeny of the individual -a particular tobacco leaf becomes discolored due to a mutation halfway through the life of the plant Gametic mutation -the mutation originates in the reproductive cells of an individual and affects their offspring -a man receives a pelvic X-ray. Nine months later, his child is born with a chromosomal abnormality Both -Mutations can be caused by an alteration in the DNA sequence

Male gametogenesis (spermatogenesis)

spermatogonia (2n) > primary spermatocyte (2n) > two secondary spermatocytes (1n) > 4 spermatids (1n)

Lyon hypothesis

states that within each female cell, one of the two X chromosomes is inactivated Xist gene inactivates X chromosome

ACAAAC to ACATAC

substitution, missense mutation

AACCTG to AACTTG

substitution, nonsense mutation

Use the information gathered in the Crossing Over in an Individual Heterozygous for a Paracentric Inversion animation to answer the question. What is the likely fate of the acentric fragment (the part not connected to the other chromatids) when the homologous chromosomes separate during anaphase I?

the acentric segment fails to segregate properly and will be lost

select the definition of aneuploidy

the addition or loss of less than a full set of chromosomes or chromosome pairs

A genetic counselor determines that patients with a deletion in a particular region of a chromosome are more likely to develop cancer than other people. Is the gene responsible for the increased risk of cancer a tumor suppressor or a proto-oncogene?

the gene is a tumor suppressor, because tumor suppressor genes induce apoptosis in abnormal cells

sex determination

the mechanism by which sex is established

Aneuploidy

the number of chromosomes is altered

In humans, what normally results in the male sexual phenotype?

the presence of the SRY gene on the Y chromosome

sex-determining region Y (SRY)

the sex-determining region of the Y chromosome,

Robertsonian translocation

the short arm of one afrocentric chromosome is exchanged with the long arm of another chromosome

DNA damage checkpoints are crucial for preventing cell proliferation when DNA damage has occurred. The role of DNA checkpoint proteins in the cell cycle is closely tied to the roles of DNA repair enzymes, although these proteins perform different functions.

these proteins pause the cell cycle if there is damaged DNA critical DNA damage checkpoints: M, G2, G1

Select the mechanisms used by tumor suppressor proteins to prevent the initiation and progression of cancer

they induce apoptosis in response to DNA damage they initiate DNA repair processes to resolve DNA damage They act at cell cycle checkpoints to regulate progression through the cycle

Triploid

three homologues of each chromosome

Which statement best describes the clonal evolution of tumors

tumor cells acquire more somatic mutations that allow them to become increasingly more aggressive in their proliferative properties

what generally causes thymine dimers to form in a strand of DNA, and why are thymine dimers a problem?

ultraviolet light can cause thymine dimers, potentially creating a mutation that could lead to cancer