Biol 1107

Exam 3

dna

one of the main components of chromatin and contains genetic information

chromatin

dna and protein complex found in eukaryotic cells. DNA is wrapped around proteins (histones) at regular intervals

chromosome

single piece of chromatin OR a replicated set of chromatin pieces that remain attached at centromere

centromere

center of chromosome

t

t/f: a single strand of chromatin is called a chromosome both originally and after replication

cell cycle

what is the event sequence during which a eukaryotic cell replicates dna and divides. lengths of gap vary

mitosis

division of nucleus that results in two identical daughter nuclei

identical daughter nuclei (2)

what is the immediate result of mitosis?

cytokinesis

division of cytoplasm that results in two daughter cells (usually occurs in conjunction with mitosis or meiosis)

does

interphase does/does not include DNA replication

interphase, cytokinesis

which 2 phases are not included as a part of mitosis

karyokinesis

the first portion of mitotic phase is called this; means nuclear division

mitosis

karyokinesis also means \______

2nd

cytokinesis is what portion of the mitotic phase?

divide the nucleus of the cell

what is the function of mitosis?

divide the cell itself

what is the function of cytokinesis?

somatic

remember that mitosis is the division of \_____ cells, so just a piece of the body.

prophase

in this stage of mitosis, chromosomes condense

prometaphase

in this stage of mitosis, nuclear envelop disintegrates (you see the nucleus slowly disappearing and the chromosomes spreading out into the entire cell)

metaphase

in this stage of mitosis, chromosomes move to the middle of the cell

anaphase

in this stage of mitosis, centromeres split and chromosomes are pulled to opposite ends

telophase

in this phase of mitosis, new nuclear envelopes will form around chromosomes. this is the end of mitosis (now have 2 identical daughter nuclei within a single cell)

cytokinesis

the process that goes along with mitosis, usually starts towards the end of mitosis (near anaphase) and ends by the time mitosis ends. cytoplasm divides into two daughter cells.

plant

which type of cells (plant or animal) builds a new cell wall and cell membrane between the two nuclei and separates that way?

animal

these type of cells have no cell wall so they just basically pinch in half almost like tightening a belt around your waist (develop a cleavage furrow)

cancer

checkpoint failures in the cell cycle can lead to \_____

end of G1 and G2, and during M phase of mitosis

when are checkpoints in the cell cycle

homologous

chromosomes of the same size and gene content that pair up during meiosis; they are the same size and shape and contain same genes

t

t/f: one of each pair of homologous genes is inherited from each parent

y

what chromosome is an exception

46 total, 23 pairs

How many chromosomes do humans have? (total and pairs)

22 pairs plus the y chromosome

what does a male's chromosomal makeup look like?

meiosis

x and y only pair up during what process?

gene

section of dna that codes for one or more related polypeptides or functional rna; this is what contains the code

alleles

different versions of the same gene

t

t/f: Homologous chromosomes from the parents contain the same genes but may not contain the same allele for those genes.

ploidy

this word refers to the number of chromosome sets present in a cell

haploid

single chromosome set (n) (ex. Gamete (like sperm) of an animal)

diploid

two chromosome sets (2n)

polyploid

greater than two sets of chromosomes (3n, 4n, 6n, etc...) - rare in animals to have more than 2 sets but very common in plants

spores; gametes

in plant cycle: meiosis produces \_______ instead of \________. then in mitosis the \________ will produce actual \_________.

diploid ploidy

in animals: offspring grow up into adults and have more offspring through sexual reproduction. an adult has a \__________ \________

haploid

gametes are \_____ because 2 gametes come together to make a full cell, so each has half the set of chromosomes the cell needs

diploid

the baby of the animal parents has \_______ ploidy because the two gametes come together and form it.

meiosis, mitosis

Adult\---\>gamete uses \______ , while baby \---\> adult uses \___________

mitosis

growth in humans happens through; we get bigger because we get more cells not because our cells get bigger

meiosis

is the division of the nucleus that results in 4 daughter nuclei that are NOT identical to each other and contain half the number of chromosomes as the original nucleus.

cytokinesis

is division of cytoplasm that results in two daughter cells - occurs twice.

t

t/f: Replication of DNA happens before the start of meiosis (same as for mitosis)

4 haploid cells

outcome of meiosis

genetic diversity

\________ \________, which is created through three major mechanisms of meiosis: independent assortment, fertilization, and crossing over

does not, because you are basically just cloning the cell.

mitosis does or does not have genetic diversity?

Independent assortment

alignments of the tetrads during metaphase of meiosis I is independent and random

Fertilization

fusion of gametes that generates an enormous amount of genetic diversity. Female and male humans each produce 8.4 million possible gametes. Two parents could deliver (8.4 million)2 genetically different offspring.

crossing over

produces new combinations of alleles in the chromosomes that did not exist in either parent.

independent assortment, fertilization, crossing over

\________ \_______, \_________, and the randomness of \_________ \_______ create an unlimited variety of gametes and offspring.

Nondisjunction

is an error that occurs during meiosis (or mitosis) in which chromosomes are incorrectly distributed among daughter cells. This is the most common error that occurs. Some daughter cells end up with too many chromosomes and some do not have enough. This happens in 20-30% of human gametes!!!

downs syndrome

The most common type of survivable nondisjunction

downs

the 21st chromosome has 3 copies instead of just 2

Klinefelter's Syndrome

Another common survivable error is when there are two X chromosomes AND a Y chromosome. This person is still male but just happens to have an extra X

turner syndrome

Another common one is when you only have one X instead of two (female)

EGGS! (Nondisjunction is far more common in eggs (70-100% of nondisjunctions occur in eggs). Most nondisjunction errors are due to the age of the mother: the older the mother, the more likely it is that their child will be born with some sort of defect or error. After age 35, a mother's chance of having a child with Down's Syndrome increases exponentially. )

Would you hypothesize that nondisjunctions are more common in eggs or sperm?

sperm

meiosis for \_________ production kicks in when puberty starts and continues until death. From the beginning of meiosis to completely mature sperm takes about 2 months. Pretty simple process, while the process for eggs is much more complicated.

female egg

only 1 of the 4 cells survives, and it is much larger than a sperm or really any other cell in the body. The one surviving cell steals resources from the other 3, which is why is it so large (can almost be seen with the naked eye).

eggs

Meiosis begins in \_____ before birth! (about 6 months before birth). Meiosis is stopped in prophase I UNTIL after puberty, when ovulation begins. One or a few eggs begin going through the rest of meiosis once a month. This is the time when the one egg starts stealing things from the rest. The smaller egg is called a polar body, and this disintegrates. Meiosis does not actually finish in an egg until after it is fertilized. Once fertilized, it divides a second time, loses another polar body, and then you have a fertilized ovum. This very different timeline than sperm is why there are so many more errors in eggs.

paradox of sex

asexual reproduction is far more efficient for producing offspring than sexual reproduction.

asexual reproduction is done by one individual, so both males and females can reproduce by themselves. In sexual reproduction, only females can reproduce. You also have the disadvantage of having to find a mate in order to sexually reproduce.

Why is it so numerically advantageous to have asexual reproduction?

results in clones so it is likely that they will not survive if environment changes

disadvantage to asexual reproduction?

Crossing over: produces new

combinations of alleles in the chromosomes that did not exist in either parent.)

dehydration

The nucleotides are put together through \______________ reactions and creates a chain.

NOT

The 5' and 3' end are \______ attached to another nucleotide.

t

t/f: the enzymes involved in replication only work in one direction.

3'

the enzymes involved in dna replication can only add nucleotides to the \______ end of the molecule

Meselson, Stahl

\________ and \_________ studied DNA replication in E. coli bacteria by using different isotopes of nitrogen (common 14N and heavier 15N) to distinguish original DNA from new DNA.

semiconservative v conservative v dispersive

meselson and stahl looked at \______ v\_____ v \________ theories

The heavy nitrogen gives you a way to be able to tell the difference between original DNA and the new DNA that has been replicated. Only the original DNA will have the 15N. (Once you transfer it to the lighter isotope, all the new DNA will have some of the 14N. So the new DNA is lighter.)

how does using the heavy nitrogen help meselson and stahl?

DNA polymerases

\____ \_________ are enzymes that catalyze the polymerization of nucleotides into DNA; can only add nucleotides to the 3' end of a DNA strand (synthesis can only proceed in the 3' to 5' direction).

dna polymerase

\___ \______ builds the DNA (very important enzyme).

Replication bubbles

\______ \_________ form in chromosomes when DNA synthesis is taking place.

Replication forks

helicases are enzymes that break hydrogen bonds between nucleotides to separate DNA strands at the \__________ \__________.

(Single-stranded binding proteins) SSBPs:

proteins that attach to separated strands of DNA and prevent them from reforming the double helix (which occurs spontaneously)& stops strands from coming back together.

Topoisomerase

this enzyme the one that relieves the tension caused by helicase. (like separating a rope: pulling it apart causes a lot of tension right beneath where it is separating and it just twists even tighter.

primers

o DNA polymerases can only add nucleotides to the 3' end of a nucleic acid and therefore require "\_________" to start replication. it adds a short RNA primer that is complementary to the DNA being copied. This template can create a 5' end.

leading

\________ strand leads into the replication fork

leading

the\________ strand is built/replicated continuously since it goes into the fork in the right direction.

bases

The\______ can be added starting at the 3' end

lagging

DNA polymerases must move away from the replication fork on the \__________ strand

lagging

The \_________ strand cannot be built in one sold piece because of its directionality.

okazaki, lagging

DNA polymerases synthesize short \_______ fragments of DNA along the \_______ strand.

rna primers, dna nucleotides

DNA polymerases then remove \_______ \___________ and replace them with \_____ \__________.

DNA ligases

\____ \________ are enzymes that catalyze bonds in DNA to finish the removal of RNA primers.

replisome

most enzymes involved in DNA replication are actually joined into one complex that moves as a unit toward the replication fork, and this is called the \_________. Lagging strand loops around the complex so the \_________ (same word) can move as a single unit.

Telomeres

are regions at the end of linear chromosomes in eukaryotes; are an issue for lagging strands

Henrietta Lacks

\___ \______ had cervical cancer and a sample of it was used (without her consent) to culture HeLa cells (named for her), which have the ability to rapidly divide because they had telomerase.

germ; embryonic stem

Telomerase is usually only active in \______ cells (produce gametes) and \________ \___________ cells

If telomeres did not shorten overtime, there would be NO limit to the number of times a cell could divide. All cells would divide indefinitely

Why is telomerase not active in all of our cells?

TELOMERASE!

How do our offspring start with telomeres (how do they have fresh, long telomeres while their parents have shorter ones)? Why do our telomeres not disappear overtime?

Senescence

Telomere length may be related to \____________

shorten

Chromosomes of most cells gradually \________ with each DNA replication and cell division because the end of the DNA cannot be replicated

repeating nonsense

Telomeres do not contain necessary genes but instead consist of \________ \_________ (human telomeres are simply repeats of TTAGGG).