Review- Test 4 Flashcards
What are the steps of DNA replication?
- unwinding of the DNA molecule
- complementary nitrogen base pairing
- joining of the DNA nucleotides
What happens in step one of DNA replication? (unwinding of the DNA molecule)
helicase unwinds the DNA molecule and breaks the hydrogen bonds between nitrogen bases, DNA template strands separate, DNA nitrogen bases are left exposed (unpaired), RNA primase adds a primer to a “promoter” region on DNA template strands to begin replication
What happens in step two of DNA replication? (complementary nitrogen base pairing)
new DNA nucleotides with their nitrogen bases diffuse into the nucleus and the nitrogen bases pair up with their complements on the DNA template strands, new DNA nucleotides with their nitrogen bases pair up with complements in a 5’ to 3’ direction according to the new strand, DNA polymerase acts as a “proof reader” to ensure that the correct nucleotide with its nitrogen base is in the proper place, hydrogen bonds form between complementary nitrogen bases
What happens in step three of DNA replication? (joining of the DNA nucleotides)
DNA polymerase catalyzes the formation of covalent bonds between adjacent nucleotides, ligase joins Okazaki fragments together (and seals “nicks”) between phosphate groups and pentose sugars
What is the purpose of DNA polymerase in DNA replication?
It catalyzes (speeds up) the formation of covalent bonds between adjacent nucleotides.
Where does DNA replication occur within the cell?
the nucleus
each new DNA molecule is composed of one original (template) DNA strand and one new strand
semi-conservative replication
properties of mitosis: location
animals: skin, liver, muscles, hair (in the dermis), stomach, etc.
plants: meristem
properties of mitosis: chromosome number
stays the same from cell to cell (46 chromosomes in humans, 104 in goldfish, etc.)
properties of mitosis: genetics
produces genetically identical cells
basic structure of a duplicated (double-stranded) chromosome
2 sister chromatids (genetically identical) and 1 centromere (holds them together)
Name the components of the cell cycle.
interphase, mitosis, cytokinesis
What are the main structures seen in a cell when it is in its Interphase state?
intact nuclear membrane, nucleolus is present, chromatin (unwound DNA + protein) present
In which part of Interphase does DNA replication occur?
S phase
Name the stages of mitosis (in order).
Prophase,
Metaphase,
Anaphase,
Telophase
What happens in prophase?
chromatin condenses into visible chromosomes, nuclear membrane begins to break down and eventually disappears, nucleolus disappears, pairs of centrioles migrate to opposite poles of the cell, spindle fibers appear, asters appear;
(centrioles and asters are only found in animal cells)
What happens in metaphase?
distinct and short-lived; centromeres of the chromosomes align themselves at the equator, spindle fiber formation is complete and the spindle fibers attach to the centromere of the duplicated chromosomes
What happens in anaphase?
centromeres of the duplicated chromosomes will split, chromatids separate and move away from one another, chromatids are now called chromosomes, chromosomes migrate to opposite poles of the cell
What happens in telophase?
chromosomes reach their poles and uncoil back into chromatin, nuclear membrane reforms around the chromatin, a new nucleolus reappears, spindle fibers disassemble and dissappear, asters disappear, cytokinesis begins
Is interphase a stage of mitosis?
no
the process by which one mother cell divides into two genetically identical daughter cells
mitosis
the division of the cytoplasm and associated cell parts (both plants and animals), occurs in very late mitosis (late anaphase/early telophase)
cytokinesis
What structure forms in plant cells during cytokinesis?
cell plate
What structure forms in animal cells during cytokinesis?
cleavage furrow
properties of meiosis: location
reproductive organs…
animals: male=testes, female=ovaries
plants: male=anthers, female=ovaries
properties of meiosis: chromosome number
reduced to one-half of the original number
humans: 46 → 23 → 23
properties of meiosis: genetics
cells are genetically variable
chromosomes that contain similar genes at corresponding loci (locations) along their length
homologous chromosomes
the homologous chromosomes pair up and exchange genetic material
crossing-over
When does crossing-over occur?
Prophase I of Meiosis I
Why is crossing-over important?
leads to a high degree of genetic variability among cells
What are the differences between mitosis, meiosis I, and meiosis II?
mitosis: chromosome number stays the same, PMAT; meiosis I (reduction division): chromosome number is reduced to half of the original, PMAT I, crossing-over; meiosis II (equational division): chromosome number is not reduced again, PMAT II
How is interphase different from interkinesis?
DNA is not replicated in Interkinesis.
If you are given the diploid number, how do you determine the haploid number?
diploid number ÷ 2 = haploid number
the production of gametes (2 types)
gametogenesis
occurs within the testes of the male to produce the sperm cell, begins at puberty in males
spermatogenesis
involves the production of the egg cell within the ovary of the female, begins prior to birth
oogenesis
Where does spermatogenesis occur?
testes (male)
Where does oogenesis occur?
ovaries (female)
What cells are produced by spermatogenesis?
sperm (1N/haploid);
undifferentiated= spermatogonium, 2N
What cells are produced by oogenesis?
egg (1N/haploid)
Who is known as the “Father of Genetics”?
Gregor Mendel
What plant did Mendel study to learn about inheritance patterns? (scientific name)
Pisum Sativum
Why did Mendel choose the plant that he did to study inheritance patterns?
easy to grow;
produced multiple offspring;
for every trait he looked at, there were only two distinguishable forms
biological unit of inheritance
e.g. coat color
gene
different forms of a gene
e.g. allele for black coat and allele for bay coat
alleles
the genetic makeup of an individual
e.g. AA / Aa / aa
genotype
the physical, observable characteristics
e.g. black coat / bay coat
phenotype
What method is used to predict the probable outcome of a genetic cross?
Punnet Square
How does meiosis differ from mitosis in location?
meiosis: reproductive organs;
mitosis: plants=meristem, humans=almost everywhere
How does meiosis differ from mitosis in chromosome number?
meiosis: reduced to one-half;
mitosis: stays the same
How does meiosis differ from mitosis in genetics?
meiosis: genetically variable;
mitosis: genetically identical
“AA” is an example of…
homozygous dominant
“Aa” is an example of…
heterozygous (dominant)
“aa” is an example of…
homozygous recessive
always written in capital letters
dominant allele
In a heterozygote, the ___ allele “masks” the presence of the ___ allele. (complete dominance)
dominant,
recessive
always written in lower case letters
recessive allele
having two different alleles for the same trait (genotype)
heterozygous
having two identical alleles for the same trait (genotype),
can be dominant or recessive
homozygous
a tool used to solve genetics problems
Punnet square
a cross between individuals who differ with respect to 1 trait or where only 1 trait is considered
monohybrid cross
a cross between individuals who differ with respect to 2 traits or where only 2 traits are considered
dihybrid cross
one allele is completely dominant over the other allele
e.g. T=red, t=white, Tt=red
complete dominance
the heterozygous phenotype is an intermediate between the dominant and recessive alleles
(e.g. T=red, t=white, Tt=pink)
incomplete dominance
the heterozygous individual fully expresses two different alleles at the same time
(e.g. Blood Type: AB / T=red, t=white, Tt=red+white)
codominance
