bio111 lecture exam 2

what is cytokinesis?

the process of dividing one cell into two

what kind of ring do animal cells use for cytokinesis?

contractile

what is a contractile ring made of?

actin microfilaments and myosin motor proteins

what is it called when the cell is pinched into two in cytokinesis?

cleavage furrow

what are vesicles?

small membrane-bound structures

what is the first step of cytokinesis in plant cells?

vesicles accumulate in the middle of the cell

what is the second step of cytokinesis in plant cells?

vesicles bring the necessary material to form a temporary structure called a cell plate

what is the third step of cytokinesis in plant cells?

the cell plate goes through a series of biochemical changes and becomes the cell wall

how many chromosomes are in a human cell during G1?

46

how many chromatids does each chromosome have in a human cell?

one

what are homologous chromosomes/homologs/a homologous pair?

a pair of chromosomes that contain the same set of genes but the genes have slightly different sequences

what does ploidy describe?

how many homologs of each chromosome an organism has per cell

what is diploid?

two homologs of each chromosome per cell(one from each parent), 2n

what is polyploid?

more than two homologs of each chromosome per cell

what ploidy are daughter cells of meiosis?

haploid

what is gametogenesis?

making sperm and egg cells

what does spermatogenesis result in?

4 viable haploid sperm cells

what does oogenesis result in?

1 mature egg cell and 3 polar bodies

what are the complexes called that are formed when homologs pair up in prophase?

bivalents or tetrads

what is crossing over?

genetic material exchanged between paired chromosomes

when can crossing over occur?

during prophase 1

can crossing over occur multiple times along chromosomes?

yes

what is independent assortment?

alignment of homologs on either side of the metaphase plate is random

why is independent assortment important?

greater genetic diversity-each new cell contains a mixture of homologs from the mother and father

what segregates the homologs during anaphase?

kinetochore microtubules

what is interkinesis?

a period of rest in preparation for meiosis 2

what is nondisjunction?

a failure of chromosomes to separate properly

when can nondisjunction occur?

in meiosis 1 or 2

what does nondisjunction lead to?

aneuploidy

what is aneuploidy?

cells have abnormal #s of chromosomes

what are the two types of attachment of kinteochore microtubules?

amphitelic and syntelic

what is normal attachment of kinetochore microtubules called?

amphitelic attachment

what is it called when kinetochore microtubules from the same spindle pole attach to both kinetochores?

syntelic attachment

what were inheritance studies like before mendel?

not quantitative

what was the accepted notion regarding genetics before mendel?

blending of inheritance

what did mendel hypothesize?

a particular unit of inheritance(genes)

what is a gene?

a portion of dna within a chromosome that contains the necessary information to influence a trait

what is it called when one gene governs a trait?

monogenic

what is it called when multiple genes govern a trait?

polygenic

what is a chromosome?

a unit of dna that contains many genes

what is a locus?

the physical location of a gene on a chromosome

what is each version of a gene called?

an allele

what is a set of alleles called?

genotype

what is the physical trait that results from a genotype called?

phenotype

what are true breeding organisms?

they always show a particular phenotype in each generation

what is a monohybrid cross?

experiment where parents are only different in one trait

what is a dihybrid cross?

experiment where parents are only different in two traits

which of mendel’s laws says that homologous chromosomes separate during anaphase 1 of meiosis, and alleles must segregate along with them?

law of segregation

what does mendel’s law of segregation imply?

only one allele of each gene can be in a gamete(diploid organisms)

simple mendelian inheritance patterns are only possible if: each trait being looked at is governed by ______

a single gene

simple mendelian inheritance patterns are only possible if: the gene governing the analyzed trait has only ______

two alleles

simple mendelian inheritance patterns are only possible if: there is a clear _______ relationship between the alleles of each gene

dominant-recessive

simple mendelian inheritance patterns are only possible if: gametes with either allele are ________

equally likely

simple mendelian inheritance patterns are only possible if: gametes combine _________

randomly

simple mendelian inheritance patterns are only possible if: each ______ is equally viable

phenotype

do most traits and alleles follow simple mendelian inheritance?

no, they are more complex

what is it called when parents with two different phenotypes can produce offspring with a third phenotype?

incomplete dominance

what is it called when a heterozygote shows both phenotypes?

codominance

what is it called when genes can affect the function of other genes and influence phenotypes?

epistasis

what is an example of epistasis?

dog coat color

what is an example of codominance?

ABO blood type

what is an example of incomplete dominance?

pink flowers from red and white

what does central dogma describe?

information flow in biological systems

what is reverse transcriptase very prone to?

errors

does every gene code for a protein?

no

what is the site where dna polymerase binds?

promoter region

what part of a gene contains the sequence that will be transcribed?

coding region

what is the area where transcription ends?

termination sequence

what are the three phases of transcription?

initiation, elongation, termination

how many types of rna polymerase are involved in transcription in prokaryotes?

one

what are the two sections of the prokaryotic rna polymerase?

sigma factor and core enzyme

what is the role of a sigma factor?

initiates transcription

what is the role of a core enzyme?

synthesizes the dna

what is a holoenzyme?

sigma factor and core enzyme together

what is the core enzyme made up of?

2 alpha subunits and 2 beta subunits

what region does the sigma factor bond to on a gene?

promoter region

when are transcription and translation coupled?

in prokaryotes

why are transcription and translation coupled in prokaryotes?

no nucleus to separate genes and ribosomes, so mRNA is translated as soon as it’s made

what is monocistronic mRNA?

contains the coding region for one gene

what does polycistronic mean?

contains the coding regions for multiple genes

where do polycistronic mRNAs come from?

gene clusters called operons

what do operons contain?

sets of genes that work together in a biological function(genes that have to be expressed simultaneously)

what do genes in an operon share?

promoter and termination regions

what is a lac operon?

a cluster of three genes involved in the transport and metabolism of lactose

where does transcription occur in eukaryotes?

nucleus

where does translation occur in eukaryotes?

cytoplasm

how many different rna polymerase enzymes are there in eukaryotes?

three

what does rna polymerase 1 do in transcription?

transcribes rRNAs

what does rna polymerase 2 do in transcription?

transcribes mRNA genes

what does rna polymerase 3 do in transcription?

transcribes tRNA and rRNA

what are eukaryotic rna polymerases missing in eukaryotic cells?

sigma factor

what proteins attach to the promoter region and attract rna polymerases?

transcription factors

what does pre-mRNA go through to become mRNA?

three steps of modification

what does adding a 7-methy-guanosine to the 5’ end of the mRNA do?

protects the mRNA from the degradation on the 5’ end

what does the addition of a poly-A tail to the 3’ end do?

protects the mRNA from degradation on the 3’ end

what are exons?

dna sequences that code for part of the protein

what are introns?

“intragenic” proteins that do not code for part of the protein

what happens in mRNA splicing?

introns are cut out and exons are spliced together

where does mRNA modifications happen?

nucleus

what enzyme does splicing?

spliceosome