exam 4 mountjoy

synapsis

The process of pairing replicated homologous chromosomes during prophase I of meiosis I

bivalent

Refers to a synapsed pair of homologous chromosomes.

chiasma

site of crossing over

late prophase I

the two homologs become attached to microtubules from opposite poles & begin to separate

crossing over between non sister chromatids

synaptonemal complex

proteins that hold together homologs

Meiosis I contains \_________________ chromosomes while Meiosis II contains \__________________.

homologous, sister chromatids

Daughter cells are \___________ after meiosis I.

haploid (n)

what occurs in meiosis but not mitosis?

synapsis of chromosomes

During which stage on meiosis does the cell go from 2n to n?

between metaphase I and anaphase I

independent assortment

the random distribution of homologs during meiosis

predict how many genetically different offspring could be produced by outcrossing two 2n \= 4 individuals.

4 × 4 \= 16

What are homologous chromosomes?

chromosomes that are similar in their size, shape, and genes are in same position along chromosomes

What is an outcome of genetic recombination?

the new combination of maternal and paternal chromosome segments that results when homologs cross over

Nondisjunction that leads to problems in offspring can occur in:

meiosis I and II

gene

hereditary factory that influenced a particular trait

allele

particular form of a gene

pure line

individuals of the same phenotype that, when crossed, always produce offspring with the same phenotype

hybrids

offspring from matings between homozygous parents with different genotypes

what did the reciprocal cross determine?

Gender has no influence on genetic determinants

If you cross two homozygous individuals, what will the genotype of each individual be?

100% heterozygous

If you cross two heterozygous individuals, what will the genotype of each individual be?

1/4 homozygous dominant \n 1/4 homozygous recessive \n 1/2 heterozygous (dom)

What is the phenotypic ratio of crossing two heterozygotes?

3:1 ratio

What is the genotypic ratio of crossing two heterozygotes?

1:2:1

The phenotypic ratio when you cross GGxGg is \__________.

no ratio because they are 100% expressing the dominant allele

The principle of segregation

Separation of alleles during gamete formation

independent assortment

alleles of different genes are transmitted independently of each other

dependent assortment

The transmission of one allele depends on the transmission of another

What is the purpose of a testcross?

by analyzing the phenotype of offspring, the unknown parental genotypes can be determined

What components go into a testcross?

parent with known phenotype but unknown genotype crossed with a parent with only recessive allele

In a dihybrid cross what is the phenotype ratio?

9:3:3:1

How many different offspring genotypes are produced from dihybrid cross?

9

Mendel's principle of segregation: \___________________; \______________________: dihybrid crosses

monohybrid crosses \n principle of independent assortment

The chromosomal theory of inheritance states that

genes are on chromosomes

The physical separation of alleles during anaphase I of meiosis is responsible for

Mendel's principle of segregation

The physical alignment of homologous chromosomes during metaphase I of meiosis is responsible for

independent assortment

wild-type allele

most common allele in a population

\___________________ is the tendency of alleles to be inherited together because they are on the same chromosome

linkage

Are genes more likely to cross over when they are far apart or when they are close together?

far apart

How can frequency of crossing over be used to create a genetic map?

the genes that have crossed over the most are more than likely farther apart on the chromosome

Are alleles always dominant or recessive?

no, codominance and incomplete inheritance

Codominance

Heterozygotes display the phenotype of both alleles

pleiotropic genes

genes that influence many traits

The genes for the traits that Mendel worked with are either all located on different chromosomes or behave as if they were. How did this help Mendel recognize the principle of independent assortment?

Otherwise, his dihybrid crosses would not have produced a 9 : 3 : 3 : 1 ratio of F2 phenotypes.

Why is the pea wrinkled-seed allele a recessive allele?

The trait associated with the allele is not exhibited in heterozygotes.

When is the full number of chromosomes restored?

fertilization

Which meiosis is known as "reductive"

meiosis I

What can nondisjunction lead to?

polyploidy

what is a meiotic error called?

nondisjunction

What stage do primary oocytes arrest? Primary oocytes are precursors to eggs

prophase 1

The\______________ hypothesis suggested that an offspring's traits are intermediate between the mother's and father's traits.

blending inheritance

Which of the following statements about an X-linked dominant disease is true?

All female offspring from an unaffected female and an affected male would have the disease.

semiconservative replication

Parental strands separate, and each is a template for a new strand,,,each daughter strand has one old and one new strand

conservative replication

the parental molecule serves as a template for an entirely new molecule,,,one daughter has both old strands, one has 2 new strands

dispersive replication

parental molecule is cut into sections,,,each daughter has new and old dispersed

DNA synthesis always proceeds in the \____ to \____ direction.

5' to 3'

What catalyzes DNA synthesis?

DNA polymerase

DNA polymerase will only add to the \___ end of the growing DNA chain

3'

DNA polymerization is \________________ because it requires energy

endergonic

A monomer used by DNA polymerase to polymerize DNA and creates phosphodiester bonds due to its high potential energy

dNTP (deoxyribonucleoside triphosphate)

What is the difference between bacterial and eukaryotic origins of replication?

bacterial cells only have one location while eukaryotes have multiple

What creates the replication fork?

helicase

DNA helicase

breaks the hydrogen bonds between the base pairs

What prevents the new single strands created after helicase from snapping back into a double helix?

single-strand DNA-binding proteins (SSBPs)

\_____________ cuts and rejoins DNA to relieve tension induced by helicase

topoisomerase

Describe the purpose of a primer.

the RNA strand that forms complementary base pairs with the DNA template strand and provides DNA polymerase with a 3' hydroxyl (-OH) group that can be linked to a deoxyribonucleotide that can be used to from phosphodiester bond

The strand that is synthesized TOWARD the replication fork is the\__________________: synthesized continuously 5′ → 3′

leading strand

The strand synthesized AWAY from the replication fork is the \________________ synthesized stepwise (5′ → 3′ direction)

lagging strand or discontinuous strand:

What supplied DNA polymerase with a 3' end to add to?

primer

What enzyme synthesizes the primer?

primase

what are the 2 parts of the leading strand synthesis?

sliding clamp- forms ring around DNA

grip- adheres to DNA strand

The lagging strand is synthesized as short discontinuous fragments called \_____________

Okazaki fragments

What links the Okazaki fragments

DNA ligase

\_____________________ removes the primers and replaces them with DNA

DNA polymerase I

replisome

Contains the enzymes responsible for DNA synthesis around the replication fork

What replicates telomeres using a RNA template that is carries and allows cell to continue diving longer

telomerase

What part of DNA polymerase detects mistakes?

proofreading

What are the three steps to synthesis at the replication fork?

(1) Helicase opens the double helix, SSBPs stabilize the exposed single strands, and topoisomerase removes twists downstream of the fork; (2) DNA polymerase synthesizes the leading strand after primase has added an RNA primer; and (3) the lagging strand is synthesized in Okazaki fragments that eventually are joined together.

How are Okazaki fragments synthesized?

using the lagging strand template, and synthesizing 5′ → 3′

mRNA

carries a genetic message out of nucleus from DNA to the site of protein synthesis

What does RNA polymerase synthesis use as a template?

DNA strand

Central Dogma

DNA codes for RNA, which codes for proteins

\____________________ is the process of using a DNA template to make a complementary RNA. (making copy of info)

transcription

\___________________ is process of using the info in mRNA to synthesize protein. (interprets nucleotide "language" to amino acids)

translation

How do alleles of the same gene differ?

In their DNA sequence

reverse transcriptase

An enzyme encoded by some certain viruses (retroviruses) that uses RNA as a template for DNA synthesis. \****exception to the Central Dogma

mRNA is complement to DNA

true

The \_____________ specifies how a sequence of nucleotides (in DNA) codes for a sequence of amino acids (in proteins)

genetic code

a group of 3 bases that specifies a specific amino acid

codon

Which of the following is an important exception to the central dogma of molecular biology?

Many genes code for RNAs that function directly in the cell.

function of helicase

unzips

function of Single Stranded DNA-Binding Proteins (SSBPs)

Stabilizes single strands

function of Topoisomerase

Relieves pressure behind the fork

function of primase

RNA primers

function of DNA polymerase I

Extends leading strand/ Okazaki fragment

function of sliding clamps

grips DNA

function of DNA Polymerase I

Removes and replaces RNA primers

function of DNA ligase

Rejoins new fragment with parent strand

function of telomerase

Replicates the end of the lagging strand

Which enzyme allows RNA to be coded into DNA?

reverse transcriptase

Trichoplax adhaerens (Tp) a simple, single celled organism are diploid (2n\=12). How many chromosomes should be found in a Tp sperm nucleus?

6