Genetics Exam 1

Mendel Proposed:

- 1 gene determines 1 character (trait) - Body cells have 2 copies of a gene, sex cells have only 1 - a gene exists in 2 forms (2 alleles for a gene)

Diploidly

- Diploid eukaryotic cells contain their genetic information in pairs of homologous chromosomes, with one member of each pair being derived from the maternal parent and one from the paternal parent. - Diploidy means that both members of a homologous pair of chromosomes are present.

What is a Barr body, and where is it found in a cell?

- It is an inactivated X chromosome. It is an inactivated Y chromosome. - There will be one less Barr body than the number of X chromosomes. - It is a darkly stained region near the nuclear envelope of interphase cells. - It is seen in nuclei of mammals with two or more X chromosomes

Shape and sizes of chromosomes:

- Metacentric- centromere in the center - Submetacentric - centromere is off center but closer to the center than the telomeres - Acrocentric - centromere is closer if off center but closer to the telomeres - Telocentric- when the centromere is at the telomere

Identify the reasons why meiosis leads to significant genetic variation while mitosis does not.

- Through independent assortment of chromosomes at anaphase I of meiosis, daughter cells may contain different sets of maternally and paternally derived chromosomes. - Crossing over happens at a much higher frequency in meiotic cells as compared with mitotic cells.

Principle of segregation

- alleles of gene separate during gamete formation

The human cycle:

- female and male gametes 2n=26 - germ cells undergo a miotic cell division called meiosis, has effect on chromosome # and takes 2 sets of chromosomes and separates them into 2 pools - gamete n=23 - fertilization - Zygote 2n=46 - zygote divide Mitotic, this does not change chromosome #

three things true of homologous chromosomes

- in a pair, one is of maternal origin, the other of paternal origin - crossover between them contributes to genetic diversity -separate during anaphase I of meiosis

prokaryotes

- less complex - Bacteria and Archea - chromosomes not contained within a membrane bound nucleus - Genetic material found in nucleoid - cell wall

Sperm cell structure

- long flagellum and head - organelle at tip known as the acrosome - this contains digestive enzymes that are released when the sprem meets and egg

Eukaryotes

- more complex - membrane bound organelles - genetic material found in nucleus - mitochondria

meiosis 1

- more complicated than mitotic cell division - 2 divisions: Meiosis 1 - reproduction division Meiosis 2 - equational division

Oogenesis

- production of eggs - occurs within diploid cells of the ovary known as oogonia - primary ooctyes goes thru meiosis to produce on cell that will become an egg - first meiotic division is asymmetrical and produces a secondary oocyte and a much smaller cell, known as a polar body. -the secondary oocyte begins meiosis II and then released from the ovary called ovulation - travels to the uterus and potentially is hit with a sperm

Principle of Dominance

- relationship between unlike alleles given 2 alleles for a gene: one dominant allele one recessive allele ex) . flower color purple - dominant white recessive

Eukaryotic Chromosome relaxed vs condensed state

- relaxed state: individual pieces NOT visible - condensed state: packaged

whats three things true about sister chromatids

- separate during anaphase II of meiosis - separate during anaphase of mitosis - contain identical nucleotide sequences prior to crossing over

structure of a Eukaryotic Chromosome

- the centromere is also the site where the kintecore forms - the ends of the chromosomes are the telomeres

chromosome structure

- the duplicated one has 2 pieces of chromatin while the single one has 1 piece of chromatin

Spermatogenesis

- the production of sperm - occurs within glands known as the testes - testes contain spermatogonial cells that divide by mitosis to produce two cells - one remains a spermatogonial cell and the other cell becomes a primary spermatocyte -4 haploid cells are produced thru meiosis known as spermatids - these then mature into sperm cells

A student is studying 3 linked genes. They are given a genotype (AA Bb Cc) and asked to provide an illustration of the chromosome(s) with these genes. This student's diagram will consist of ________ homologous pair(s) of chromosomes?

1 homologous pair - when two or more genes are linked they are located on the same chromosomes

Indicate the expected number of Barr bodies in interphase cells of individuals with the following karyotypes. 1) 46 XX. 2 ) Klinefelter syndrome. 47 XXY 3) 47 XXX. 4) 48 XYYY.

1) 1 2) 1 3) 2 4) 0 (always 1 less bar body than there are Xs)

The nuclear DNA content of a single sperm cell varies depending on the species of the organism. If the amount of DNA in a single sperm cell is 1.95 picogram(s), calculate the amount of DNA at different stages of meiosis or mitosis. 1) What would be the expected nuclear DNA content of a primary spermatocyte in the same organism? 2) What would be the expected nuclear DNA content of a somatic cell (non-sex cell) in the G1 phase? 3) What would be the expected nuclear DNA content of a somatic cell at metaphase? 6.2 picograms

1) 1.95 x 4 = 7.8 2) 1.95 x 2 = 3.9 3) 1.95 x 4 = 7.8

********The diploid number of chromosomes in the mustard plant is 10. 1) How many chromosomes will be found in each cell during prophase? 2) How many DNA molecules will be found in each cell during prophase? 3) How many chromosomes will be found in each cell at the end of anaphase? 4) How many DNA molecules will be found in each cell at the end of anaphase? 5) How many chromosomes will be found in each cell after telophase/cytokinesis is completed? 6) How many DNA molecules will be found in each cell after telophase/cytokinesis is completed?

1) 10 chromosomes 2) 20 molecules 3) 20 chromosomes 4) 20 molecules 5) 10 chromosomes 6) 10 molecules

If one follows 80 primary oocytes in an animal through their various stages of oogenesis, 1) how many secondary oocytes would be formed? 2) how many polar bodies? 3) How many ootids?

1) 80 2) 80 3) 80

If one follows 80 primary oocytes in an animal through their various stages of oogenesis, 1) how many secondary oocytes would be formed?

1) 80 x 2 = 160 2) 80 x 4 = 320

a eukaryotic cell has the capacity to divide, what are the three stages it goes through and what happens in each stage?

1) Mitosis - it replicates all of it's genetic material 2) Meiosis I - dividing the replicated genetic material into two pools 2) Meiosis - separation of two pools by dividing the cytoplasm, creating daughter cells

1) Contrast the genetic content and the origin of sister versus nonsister chromatids during their earliest appearance in prophase I of meiosis. 2) How might the genetic content of these change by the time tetrads have aligned at the metaphase plate during metaphase I of meiosis?

1) Sister chromatids are genetically identical, except where mutations may have occurred during DNA replication. Nonsister chromatids are genetically similar if on homologous chromosomes and genetically dissimilar if on nonhomologous chromosomes. 2) If crossing over occurs, then chromatids attached to the same centromere may no longer be identical.

A diploid somatic cell of an organism contains 36 chromosomes (total). How many non-homologous chromosomes are associated with the genome of the organism?

18

How many haploid sets of chromosomes are present in a diploid individual cell with a chromosome number of 32? 46?

2

The house fly, Musca domestica, has a haploid chromosome number of 6. How many chromatids should be present in a diploid, somatic, metaphase cell?

24

In an organism with 52 chromosomes, how many bivalents would be expected to form during meiosis?

26

A diploid somatic cell of an organism contains 36 chromosomes (total). How many chromatids are present in a secondary oocyte of this organism?

36

Jacobs syndrome in humans, which is manifested by a higher than average stature and potential behavioral problems, is caused by which chromosomal condition?

47, XYY

How many haploid sets of chromosomes are present in an individual cell that is pentaploid (5n)?

5

The horse (Equus caballus) has 32 pairs of chromosomes, whereas the donkey (Equus asinus) has 31 pairs of chromosomes. How many chromosomes would be expected in the somatic tissue of a mule, which is a hybrid of these two animals?

63

CHAP 2: what is a homolog, with regards to genes and alleles how are they similar/different from each other?

A homolog refers to the members of a chromosome pair. They are the same size and carry the same types and orders of genes. They may differ in that the genes they carry may be different alleles

CHAP: with regard to genotypes, what is a true-breeding organism

A homozygote that has two copies of the same allele

In what Phase of the cell cycle - G1, S, G2, prophase, metaphase, anaphase, or telophase - would you expect somatic cells to stay if the following types of drug were added A) a drug that inhibits microtubule formation B) a drug that allows microtubules to form but prevents them from shortening C) a drug that inhibits cytokinesis D) a drug that prevents chromosomal condensation

A) G2 B) Metaphase C) Telophase D) G2

?CHAP 2: Specify weather the following events occur in Mitosis, Meiosis I or Meiosis II A) seperation of conjoined chromatids within a pair of sister chromatids B) pairing of homologous chromosomes C) alignement of chromatids along the metaphase plate D) attachement of sister chromatids to both poles

A) Mitosis and Meiosis II B) Meiosis I C) all 3 D) Meiosis I and Meiosis II

*****Which of the following pairs of chromosomes has the same amount of DNA? a. An unreplicated chromosome and a chromatid b. Two nonhomologous chromosomes c. A replicated chromosome and a sister chromatid d. A replicated chromosome and a bivalent e. All of the above are pairs that have equal amounts of DNA

A. An unreplicated chromosome and a chromatid

________are those structures formed by the synapsis of homologous chromosomes.

Bivalents

________refers to the structure, when viewed microscopically, of crossed chromatids.

Chiasmata

During interphase, most of the nucleus is filled with a complex of DNA and protein in a dispersed form called

Chromatin

Chromosomes are made of what?

Chromatin = DNA + Protein + RNA

_______is the exchange of genetic material between chromatids.

Crossing over

when does crossing over occur?

Crossing over occurs during early prophase I when homologous chromosomes loosely pair up along their lengths. Crossing over occurs only between nonsister chromatids within a homologous pair of chromosomes, not between the sister chromatids of a replicated chromosome. Crossing over is reduced near the centromere; segments that are not adjacent to the centromere (for example, segments near the ends of chromosomes) are more likely to cross over.

*****Mendel's Principle of Independent Assortment states that the alleles of different genes will distribute randomly (or independently) of one another during the formation of gametes. When is independent assortment set in place (i.e. when is it established)? (0.6) a. Mitosis or Meiosis I b. Mitosis and Meiosis II c. Meiosis I or Meiosis II d. Meiosis I e. Meiosis II

D. Meiosis

The parent cell that enters meiosis is diploid, whereas the four daughter cells that result are haploid: describe how cellular DNA content and ploidy levels change during meiosis I and meiosis II? (Note: Ignore any effects of crossing over.)

DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II.

Chromosomes are made of ___________ and all of them together constitute the cell's nuclear _______________. They are also located on the _________

DNA, Chromatin, nucleus

CHAP: Describe Mendal's Law of segregation

Diploid organisms contain two copies of each type of gene. When they make gametes, only one copy of each gene is found in a gamete. Two alleles cannot stay together within the same gamete.

Predict the potential effect of the Lyon hypothesis on the retina of a human female heterozygous for the X-linked red-green color blindness trait.

Females will display mosaic retinas with patches of defective color perception and surrounding areas with normal color perception.

# of chromosomes per cell, # of DNA molecules per cell, # of chromatids per cell

G1 - 4,4,0 S - 4,8,8 G2 - 4,8,8 Prophase + Prometaphase - 4,8,8 Metaphase - 4,8,8 Anaphase - 8,8,0 Telophase + Cytokinesis - 4,8,0

CHAP 2: a spieces is diploid containing three chromosomes per set. How many chromosomes will there be in G1, G2 phases of the cell cycle?

G1- 6 linear chromosomes G2- 12 chromatids that are attached to each other in pairs of sister chromatids - so 6 chromosomes

Gametes are highly specialized cells that are produced by the process called

Gametogenesis

If two chromosomes of a species are the same length and have similar centromere placements and yet are not homologous, what is different about them?

Genetic content, the banding pattern, and time of replication during S phase.

two types of cells in the body

Germ Cells - ultimately gonna produce reproductive cells - gametes (located in the reproductive track) Somatic Cells - any cell other cell in the body (not gametes or germ cells)

If a cell goes through Meiosis, what kind of cell is it?

Germ cell

Dploid (2n) vs Haploid (n)

Haploid - the number of nonhomologous chromosomes that define a chromosome set for a given species - for humans: 23 Diploid - 2x the haploid - for humans: 46

Haploidy

Haploidy specifically refers to the fact that each haploid cell contains one chromosome of each homologous pair of chromosomes.

hemizygous

Having only a single copy of a gene instead of the customary two copies. All the genes on the single X chromosome in the male are 'hemizygous.

compare and contrast Homologous Chromosomes

Homologous chromosomes are a pair of chromosomes, one maternal and one paternal, that come together during fertilization. They have the same centromere position, and the same genetic loci (genes); however the DNA sequence is not identical. Crossing over between homologous chromosomes during prophase I of meiosis generates genetic diversity in the offspring. Homologous chromosomes pair up along the midline during metaphase I of meiosis, and move apart during anaphase I. Sister chromatids are the result of the replication of a single chromosome. They are identical in DNA sequence (apart from mutation or crossing over with a chromatid from a homologous chromosome). During metaphase of mitosis, chromosomes line up down the midline and sister chromatids separate during anaphase. In meiosis, sister chromatids separate during meiosis II.

Which of the following statements about autosomal recessive traits is true?

If neither parent expresses the trait, but the offspring does, both parents must be heterozygous for the trait.

major difference between sex determination in Drosophila and in humans?

In Drosophila, the ratio of X chromosomes to the number of haploid sets of autosomes determines the sex while in humans the presence of the Y chromosome determines maleness.

Define the Lyon hypothesis.

Inactivation of an X chromosome occurs at random early in embryonic development. Inactivated X chromosomes are in some way "marked" such that all clonally related cells have the same X chromosome inactivated.

reproduction of of somatic cells - the cell cycle and mitosis

Interphase: - G1: chromosome uncondensed and unreplicated - 2n - S: chromosome uncondensed and REPLICATED and now consists of 2 sister chromatids - 2n - G2: same as S Mitotic (M): > Mitosis - - Prophase: chromatid begins to condense, lose nucleolus, nuclear membrane begins to disinergrate, centrosomes begin to move apart to opposite sides of the cell and in process they will make microtubulars, known as spindle fibers. Spindle fibers will eventually interact with kintecore protein. - Prometaphase: push/pull chromosomes around cell - Metaphase - when all chromosomes are lined up down the middle of the cell - Anaphase - sister chromatids pulled apart ( once separated they are called daughter chromosomes) - Telophase - reverse of prophase

when does crossing over occur?

It occurs between prophase 1 and metaphase 1 of meiosis.

Genes each have a ___________ that specifies it's position on _______________

Locus, chromosomes

During which part of meiosis (meiosis I or meiosis II) do the two alleles of a gene separate? During which phase does the separation occur?

Meiosis I, Anaphase

Meiosis

Meiosis involves two sequential cellular divisions. In meiosis I, homologous chromosomes pair and then separate. Thus, although the parent cell is diploid (containing two chromosome sets, one maternal and one paternal), each of the two daughter cells is haploid (containing only a single chromosome set). In meiosis II, the sister chromatids separate. The four daughter cells that result are haploid

CHAP 2: an eukaryotic cell is diploid, containing 10 chromosomes, for mitosis and meiosis - how man daughter cells would be produced and how many chromosomes would each contain?

Mitosis - 2 diploid cells, 10 chromosomes each Meiosis - 4 haploid cells, 5 chromosomes each

A sister chromatid is also called

Monad

Can the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene?

No. Why: One cannot test the Lyon hypothesis with homozygous X-linked genes because the test requires identification of allelic alternatives to see differences in X chromosome activity.

the arms of the chromosome

P arm - short arm q arm - long arm

Chromosome Number: Diploid vs Haploid

Ploid- greek for set prefix - tells you # of sets Di- 2 Hi-1

Which term describes the individual in a pedigree whose phenotype was first brought to the attention of a medical researcher?

Proband

What is the most likely mode of transmission for a trait that is not expressed in parents but is expressed by one half of the sons?

Rare X-linked recessive (mother must have been heterozygous)

A small part of the human Y chromosome contains the gene that is responsible for determining maleness. What is the name of this gene?

SRY (sex determining gene on the Y chromosome)

Cat breeders are aware that kittens expressing the X-linked calico coat pattern and tortoiseshell pattern are almost invariably females. Which one of the following statements supports this conclusion?

Since females normally have two X chromosomes, random X inactivation during development of a heterozygous female will create a mottled pattern. Normal males are not mottled, because they only have one X chromosome and therefore can only express one of the two potential X-linked alleles.

_______ are the "post-S phase" structure of replicated chromosomes. Because they are composed of two chromatids joined by a centromere, they are also called ___________

Sister Chromatids, Dyads

if a cell goes through Mitosis, what type of cell is it?

Somatic cell

Which of the following statements is an example of independent assortment?

Some genetic traits are more likely to be inherited than others

______the point-by-point pairing of homologous chromosomes during prophase of meiosis I

Synapsis

_____are synapsed homologous chromosomes, which are composed of four chromatids.

Tetrads

CHAP: difference between genotype and phenotype

The genotype is the type of genes that an individual inherits while the phenotype is the individual's observable traits.

CHAP 2: The process of binary fission begins with a single mother cell and ends with two daughter cells. Would you expect the mother and daughter cells to be genetically identical? Explain

They are genetically identical, barring rare mutations, because they receive identical copies of the genetic material from the mother cell.

Holandric

Trait controlled by a gene found only on the Y-chromosome

allele symbol

W - purple w - white flowers

calico cat genotype

XBXb (they can only be females) XB - orange Xb - black

when a germ cell enters meiosis what is it called

a primary meiocyte

somatic cells are formed from what?

a zygote or other somatic cells

Which chromosome has a telomere but the p arm is much shorter than the q arm?

acrocentric

When do sister chromatids separate during meiosis?

anaphase II

Phenotype

appearance/variants

What characteristics do two homologous chromosomes share?

autoradiographic pattern similar banding patterns overall length position of the centromere type and location of genes

After chromosomes condense, the ________________ is the region where the identical DNA molecules are most tightly attached to each other.

centromere(s)

The _____________are the organizing centers for microtubules involved in separating chromosomes during mitosis.

centrosome(s)

DNA when complexed with protein is called __________ and in it's condensed form it is called ______________

chromatin, chromosomes

what are the two forms of chromosomes?

circular (in prokaryotes) and linear ( in Eukaryotes)

In most eukaryotes, division of the nucleus is followed by , __________when the rest of the cell divides.

cytokinesis

*****A somatic cell of a diploid organism contains 36 chromosomes. How many chromosomes are present in a secondary oocyte? (0.6) a. 144 b. 72 c. 36 d. 18 e. 9

d. 18

what is the binomial expansion equation and what do you use it for

determines the probability that a certain portion will be produced with particular characteristics

when do alleles of a gene separate during meiosis?

during Meiosis I

Pedigrees: X linked Recessive

every female with trait, her father and all her sons must have that trait

Pedigrees: X-linked dominant

every male with the trait, his mother and all his daughters must have the trait

Sexual reproduction

gametes are made that contain half the amount of genetic material. theses gametes fuse with each other in the process of fertilization to begin the life of a new organism.

DNA are made up of ____________ that encode for heritable characteristics called____________

genes, traits

Pedigrees: Y linked

if a father is affected than all his sons would be affected

?CHAP 2: difference between the attachment of kinetochore microtubules to the kinetochore in Metaphase of Meiosis I and Mitosis

in Meiosis I each pair of chromatids is attached to one pole and in mitosis they are attached to both pole.

Which of Mendel's postulates can only be demonstrated in crosses involving at least two pairs of traits?

independent assortment

In dividing cells, most of the cell's growth occurs during _______________

interphase

During mitosis, microtubules attach to chromosomes at the ___________

kinetochore(s).

Linked gene vs. unlinked gene

linked genes - if located on the same chromosome unlinked genes - not located on the same chromosome

Locus/Loci

location of position of gene on the chromosome

CHAP 2: The arrangement of homologs during metaphase of meosis is a random process . What does this mean?

maternally derived and paternally derived chromosomes are randomly aligned along the metaphase plate

hetermorphic

meaning that the sprophytes and gametophytes are structurally different (males in humans are hetermorphic) XY

homomorphic

meaning that the sprophytes and gametophytes are structurally the same (females in humans) XX

The __________ is a cell structure consisting of microtubules, which forms during early mitosis and plays a role in cell division.

mitotic spindle(s)

genotype

possible allele combinations

Heterogamous

produce two metaphorically different types of gametes. male gametes (sperm cells) and female gametes (egg cell or ovum)

pseudoautosomal region

regions of Homology found on both X and Y chromosomes

heterogametic

sex chromosomes are of different types (XY)

DNA replication produces two identical DNA molecules, called ______________, which separate during mitosis.

sister chromatid(s)

Principles of independent assortment

the alleles of different genes will distribute independently of one another during gamete formation

Isogamous

the gametes are morphologically similar. Examples of isogamous organisms include many speices of fungi and algae

CHAP 2: Describe the Key events in Meiosis that result in 50% reduction in the amount of genetic material per cell

the reduction occurs because there is a single DNA replication event but TWO cell divisons, because of the nature of separation during anaphase I, each cell receives one copy of each type of chromosome.

*******tetraploid

there are four copies of every different (i.e. non-homologous) chromosome present.

diploid cell contains 6 chromosomes, how many possible random arrangements of homologs could occur during metaphase of meiosis?

three sets of chromosomes so 2^3 = 8

nonhomologus vs homologous

to be homologous three things have to be the same: length, shape, same genes that code for the shame traits - b and B are different versions of the same gene so that is acceptable for homologous

Pedigrees: Recessive

usually look for 2 unaffected parents having an affected child

gene

very specific nucleotide sequence thats located on the DNA Chromosome and codes for a functional product

How is RNA formed

when a gene is transcribed