exam 3 (practice questions) Flashcards
what is a karyotype?
organized image of a cells chromosomes
what defines a genome?
complete set of an organism’s genes and other DNA sequences
asexual reproduction occurs in which process?
mitosis
in sexual reproduction, individuals transmit _______ of their nuclear genes to each of their offspring
half
at which stage of mitosis are chromosomes usually photographed in the preparation of a karyotype?
metaphase
chromosomes are most condensed and visible, making it easier to observe and photograph them
what are 3 characteristics that all sexual life cycles have in common?
meiosis, fertilization, and gametes
gametophytes and sporophytes
gametophyte: haploid, gamete producing phase of plants and some algae (specialized cells that allow organisms to reproduce)
sporophyte: diploid, spore-producing phase of plants and some algae
alternation of generations
alternation of generations is a life cycle pattern found in certain plants and algae where two distinct phases, the sporophyte and gametophyte, alternate in a regular sequence
a diploid plant (sporophyte) produces a spore by meiosis that gives rise to a multicellular, haploid pollen grain (gametophyte)
an organism with 46 chromosomes in its karyotype produces gametes with how many chromosomes?
23
what mainly occurs during meiotic anaphase and what is a possible result of if it goes wrong?
phase in meiosis where chromosomes are separated and segregate to opposite poles of the cell
- going wrong during this time can cause incorrect amount of chromosomes in a human zygote
in a human karyotype, chromosomes are arranged in 23 pairs. if we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?
length, centromere position, staining pattern, and traits coded for by their genes
what characteristic do homologous chromosomes exhibit?
they carry information for the same traits
if meiosis produces haploid cells, how is the diploid number restored for these types of organisms?
by fertilization
which statement is correct regarding the human X chromosomes?
they carry genes that determines an individual’s biological sex
if a cell has completed meiosis I and the first cytokinesis, and is just beginning meiosis II, what is an appropriate description of its genetic contents?
it has half the amount of DNA as the cell that began meiosis
what statement describes the chromosomal makeup of each daughter cell after telophase of meiosis I?
the cells are haploid, and the chromosomes are each composed of 2 chromatids
sister chromatids vs nonsister chromatids
chromatids are one of the 2 joined chromosomes
main difference: whether chromatids are copies of the same chromosome (sister chromatids) or come from different chromosomes with similar genetic information (non-sister chromatids)
- sister chromatid separated and distributed to daughter cells during mitosis and meiosis II
-non-sister chromatids can undergo genetic recombination during meiosis I through crossing over
how do cells at the completion of meiosis compare with cells that are in prophase of meiosis I?
the cells have 1/2 the number of chromosomes and 1/4 the amount of DNA
what event happens at the conclusion of meiosis I?
sister chromatids are separated
during which process do sister chromatids separate from each other?
during mitosis and meiosis II
which process occurs in meiosis but not in mitosis?
synapsis of chromosomes
synpasis: homologous chromosomes pair up during meiosis and exchange genetic material
what is chiasmata & what stage are they first seen?
physical crossover points where the homologous chromosomes cross over and exchange genetic material
first seen in prophase I
at what stage of meiosis does the following occur:
homologous chromosomes are aligned at the equator of the spindle
metaphase I
at what stage of meiosis does the following occur:
centromeres of sister chromatids disjoin and chromatids separate
anaphase II
what is the major difference between meiosis II and mitosis in a diploid animal?
meiosis II occurs in a haploid cell, while mitosis occurs in diploid cell
what is the major difference between meiosis I and mitosis in a diploid animal?
sister chromatids separate in mitosis, while homologous pairs of chromosomes separate in meiosis I
crossing over of chromosomes normally takes place during which process? (mitosis, meiosis I, meiosis II)
meiosis I
during which process do homologous pairs of chromosomes align adjacent to one another at the metaphase plate of a cell?
metaphase I of meiosis
in which process of meiosis do centromeres split and sister chromatids migrate to opposite poles of the cell?
anaphase II
in which process does independent assortment of chromosomes occur?
in meiosis II only
independent assortment: random arrangement and segregation of homologous chromosomes along the metaphase plate
independent assortment of chromosomes is a result of which of the following processes?
the random way each pair of homologous chromosomes lines up at the metaphase plate during meiosis I
which process occurs when homologous chromosomes cross over in meiosis I?
corresponding segments of non-sister chromatids are exchanged
a human cell containing 22 autosomes and a Y chromosome is
a sperm
meiosis II is similar to mitosis in that
sister chromatids separate during anaphase
which of the following statements is correct in describing the terms monohybrid cross and dihybrid cross?
a dihybrid cross involves organisms that are heterozygous for 2 characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied
what was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
traits are inherited in discrete units and are not the result of “blending”
the individual with genotype AaBbCCDdEE can make many kinds of gametes. which of the following correctly describes why this situation is possible?
different possible assortment of chromosomes into gametes occurs
mendel continued some of his experiments into the F2 or F3 generation in order to ______________
observe whether or not a recessive trait would reappear
what explains the fact that all 7 of the pea plant traits studied by Mendel obeyed the principle of independent assortment?
all of the genes controlling the traits behaved as if they were on different chromosomes
which inheritance pattern describes the ability of a single allele to have multiple phenotypic effects?
pleiotropy
example of polygenic inheritance
skin pigmentation in humans
what statement is correct regarding gene linkage?
the closer 2 genes are on a chromosome, the lower the probability that a crossover will occur between them
which statement describes the correct meaning of the chromosome theory of inheritance as expressed in the early 20th century?
mendelian genes are at specific loci on the chromosome, and in turn, segregate during meiosis
who will carry an X-linked allele from a man who carries it?
all of his daughters (he passes X chromosome to daughter and Y to sons so no sons get it)
what does recombination frequency suggest and what does a recombination frequency of 50% and 0% mean?
likelihood of genetic recombination between genes on the same chromosome during meiosis
**recombination frequency of 0% = complete linkage (no crossing over),
frequency of 50% = independent assortment (genes are located on different chromosomes)**
what phrase correctly defines what one map unit is?
a 1% frequency of recombination between 2 genes
one possible result of chromosomal breakage is for a fragment to join a nonhomologous chromosome. what is this type of chromosomal alteration called?
translocation
which of the following facts did Hershey and chase make use of in trying to determine whether DNA or protein is the genetic material?
DNA contains phosphorus, whereas protein does not
who discovered that amounts of thymine, adenine, guanine, and cytosine are equal?
erwin chargaff
what characteristic of DNA is responsible for the vast amount of information it carries?
the sequence of bases
what is meant by “antiparallel” regarding DNA strands?
the 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand
In E. coli, which enzyme catalyzes the elongation of a new DNA strand in the 5’ to 3’ direction?
DNA polymerase III
in E. coli, to repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
nuclease, DNA polymerase, DNA ligase
In E. coli, what is the function of DNA polymerase III?
to add nucleotides to the 3’ end of a growing DNA strand
what is the difference between the leading and lagging strands of DNA during DNA replication?
the leading strand is synthesized in the same direction as the moment of the replication fork, while the lagging strand is synthesized in the opposite direction
what is the function of the enzyme topoisomerase in DNA replication?
relieving strain in the DNA ahead of the replication fork caused by the untwisting of the double helix
who performed classic experiments that supported the semi conservative model of DNA replication?
Watson and crick
the elongation of the leading strand during DNA synthesis….
depends on the action of DNA polymerase
in a nucleosome, the DNA is wrapped around
histones
transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?
several transcription factors
TATA box in promoters of eukaryotes
recognition site for the binding of specific transcription factor
in the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
the various domains of polypeptide product
how does the primary transcript in the nucleus compare to the functional mRNA?
the primary transcription is larger than the mRNA
during the elongation phase of translation, which site in the ribosome represents the location where a codon is being read?
A site
what effect would a nonsense mutation have on a gene?
introduces a premature stop codon into the mRNA
in eukaryotic cells, transcription cannot begin until
several transcription factors have bound to the promoter
which component is not directly involved in translation?
DNA
which molecule helps to “turn off” genes in a cell?
corepressor
how does transcription of structural genes in an inducible operon occur?
it starts when the pathway’s substrate is present
muscle cells differ from nerve cells mainly because they
express different genes
the functioning of enhancers is an example of
transcriptional control of gene expression
what is an example of post-transcriptional control of gene expression?
the removal of introns and alternative splicing of exons
what would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
continuous transcription of the operon’s genes
the presence of proto-oncogenes is explained by what
they normally help regulate cell division
