UNIT 1 EXAM - CH 10 - Genetics

how do telomeres prevent shortening?

1. protect chromosomes from digestion - enzyme exonuclease 2. unusual DNA replication- occurs at the telomere to make sure the chromosomes do not get shortened each round of rep

microdomains are typically how many base pairs in length? & they typically have how many of them?

10, 000 & 400-500

the lower clamps and cuts and the upper jaw is passed through a double stranded break & then its ligated back together - what is made after this has happened?

2 supercoils are made & introduced into the DNA molecule

30 nm fibers shorten dan by how much?

7 fold

how large are macro domains?

800 to 1000 kbp's in length

Which of the following is an example of a moderately repetitive sequence? rRNA genes Most protein-encoding genes Both a and b None of the above

A

chromosome?

are the structures within living cells that contain the genetic material

telomeres are located where and contain what?

at the ends of chromosomes and contain specialized sequences

nucleosome?

double stranded segment of dan wrapped around the octamer of histone proteins

The chromosomes of eukaryotes typically contain: a few hundred to several thousand different genes. multiple origins of replication. a centromere. telomeres at their ends. all of the above.

e - all of the above : ) Great job!!! KEEP GONG YOU CAN DO THIS!

telomeres?

ends of the chromosomes necessary in replication and stability of the chromosome

in bacterial cells, the nucleoid is not in a separate compartment surrounded by a membrane unlike that of?

eukaryotic cells

centromere?

forms the recognition site for the kinetochore proteins

moderately repetitive sequences?

found a. few hundred to several hundred thousand times in a genome

highly repetitive sequences?

found tens of thousands or even millions of times throughout the genome - each copy of highly repetitive sequence is relatively short and is only a few nucleotides to several hundred in length

in eukaryotes, what is the genome like?

genetic material can be found in different cellular compartments

30 nm fiber solenoid model?

helical structure, nucleosomes produce a symmetrically compact structure

where do eukaryotic cells keep their chromosomes?

in the nucleus

nucleoid

inside of a bacterial cell, a chromosome is highly compacted and found within this region

Why are chromosomes longer in eukaryotes?

introns - noncoding intervening sequences

nuclear lamina

is a collection of filaments that line the inner nuclear membrane.

kinetochores?

is composed of a group of proteins that link the centromere to the spindle apparatus

internal nuclear matrix

is connected to the nuclear lamina and fills the interior of the nucleus - fine network of irregular protein filaments with many other proteins bound to them

primary function of genetic material?

is to store information need to produce the characteristics of an organism

what does condensing do?

it coats the individual chromatids and brings the loops closer together and holds them in place

How does topoisomerase I relax negative supercoiling?

it cuts it unwinds it and then repairs it

euchromatin?

less compacted regions of the chromosome & are capable of gene transcription

eukaryotic chromosomes are usually?

linear

zig zag model?

linker regions within the 30 nm structure are bent and twisted and low face to face contact occurs between nucleosomes

circular chromosomal dna is compacted by?

loop domains

how many origins of replication are in each chromosome?

many

loops that emanate from the core are called?

micro domains

protein encoding genes?

account for the majority of bacterial DNA

DNA compacting and supercoiling make the bacterial chromosome what?

more compact to fit into the nucleiod of the bacterial cell

The chromosomal DNA of living bacteria is what?

negatively supercoiled

intergenic regions?

nontranscribed regions of DNA located between adjacent genes

What three regions are required for chromosomal replication and segregation?

origin of replication, centromeres, and telomeres.

a centromere with a defined DNA sequence is called?

point centromere

NAPs help to do what in a chromosome?

promote compaction and organization

cohesin

promotes the binding between sister chromatids

proteins from the nuclear matrix are involved in compacting the DNA into ?

radial loop domains

facultative heterochromatin

refers to chromatin that can occasionally interconvert between heterochromatin and euchromatin.

constitutive heterochromatin

refers to chromosomal regions that are always heterochromatic and permanently inactive with regard to transcription.

genome?

refers to the entire complement of genetic material in an organism or species

centromeres found in much more complex eukaryotes are called?

regional centromeres

centromeres?

segregate chromosomes during mitosis and meiosis, and also function asa site for the formation of kinetochores

eukaryotic chromosomes usually occur in?

sets

tandem arrays?

short repetitive dan sequences

transposable elements?

short segments of DNA that have the ability to move within a genome

DNA Supercoiling

since DNA is already two strands coiled around each other - the formation of additional coils due to twisting forces is due to the supercoiling

circular chromosomal dna is further compacted by?

supercoiling

chromatin is what?

the eukaryotic protein complex found in eukaryotic chromosomes

third level of compaction requires ?

the interactions between 30 nm fibers and network proteins called the nuclear matrix

what is a down side of negative supercoiling in DNA strands?

the it can promote strand separation in small regions

HI?

the linker histone - binds dan in linker region and may help to compact local nucleosomes

what makes up the nuclear matrix?

the nuclear lamina and the internal nuclear matrix

origin of replication

the nucleotide sequence that functions as an initiation site for the assembly of several proteins required for DNA replication

sequence complexity is?

the number of times a particular base appears throughout the genome of a species

histone proteins needed for what?

the structure of chromosomes

DNA gyrase is?

an enzyme that introduces negative supercoils by using energy from ATP

exons?

are regions of the RNA molecule that remain after splicing has removed the introns

each eukaryotic chromosome contains what?

A long, linear DNA molecule that is typically tens of millions to hundreds of millions bps in length

In Noll's experiment to test the beads-on-a-string model, exposure of nuclei to a low concentration of DNase I resulted in: a single band of DNA with a size of approximately 200 bp. several bands of DNA in multiples of 200 bp. a single band of DNA with a size of 100 bp. several bands of DNA in multiples of 100 bp.

B

Negative supercoiling may enhance activities like transcription and DNA replication because it: allows the binding of proteins to the major groove promotes DNA strand separation. makes the DNA more compact. causes all of the above.

B

A chromosome territory is a region: along a chromosome where many genes are clustered. along a chromosome where the nucleosomes are close together. in a cell nucleus where a single chromosome is located. in a cell nucleus where multiple chromosomes are located.

C

The role of cohesin is to: make chromosomes more compact. allow for the replication of chromosomes. hold sister chromatids together. promote the separation of sister chromatids.

C

A bacterial chromosome typically contains: a. a few thousand genes. b. one origin of replication. c. some repetitive sequences. d. all of the above.

D

DNA gyrase: promotes negative supercoiling. relaxes positive supercoils. cuts DNA strands as part of its function. does all of the above.

D

Mechanisms that make the bacterial chromosome more compact include: the formation of micro- and macrodomains. DNA supercoiling. crossing over. both a and b.

D

The compaction leading to a metaphase chromosome involves which of the following? The formation of nucleosomes The formation of the 30-nm fiber Anchoring and further compaction of the radial loops All of the above

D

With regard to the 30-nm fiber, a key difference between the solenoid and zigzag models is: the solenoid model suggests a helical structure. the zigzag model suggests a more irregular pattern of nucleosomes. the zigzag model does not include nucleosomes. both a and b are correct.

D

How does DNA become supercoiled?

DNA Gyrase

supercoiling is under the regulation of?

DNA gyrase and topoisomerase

how are micro and macro domains formed?

NAPs (nucleoid associated proteins)

what do cohesin and condensing both have?

SMC proteins

repetitive sequences play a role in?

dna folding, gene regulation, and genetic recombination

a bacterial chromosome usually only has - how many different genes?

a few thousand

in eukaryotes, what type of genome do we have?

a mitochondrial genome

NAPs are also help do what?

bend the DNA to act as bridges that cause different regions of dan to bind to each other & help with chromosome segregation as well

What are the components of a single nucleosome? About 146 bp of DNA and four histone proteins About 146 bp of DNA and eight histone proteins About 200 bp of DNA and four histone proteins About 200 bp of DNA and eight histone proteins

c

what shape is a bacterial chromosomal DNA usually in?

circular - but it can be linear

prior to metaphase what is found outside of the nucleus?

condensin

histone protein?

consists of globular domain and a flexible charged amino terminus

Loop domains are held in place by

dna binding proteins

repetitive sequences

these sequences are found in multiple copies and are usually interspersed within the intergenic regions throughout the bacterial chromosome

DNA Gyrase and topoisomerase I do what to compact it?

they introduce twists by coiling on to itself

heterochromatin?

tightly compacted regions of chromosomes that are usually transcriptionally inactive

Supercoiling helps with what?

to further compact the microdomain

Whats the function of quinolone and coumarins?

to inhibit gyrase and other topoisomerase and block bacterial cell growth

what is the function of topoisomerase I?

to relax positive supercoils

DNA gyrase. is also useful in?

untangling DNA molecules

in bacteria, what is the genome like?

usually a single circular chromosome

retroelement?

which is transcribed into RNA, copied into DNA and inserted into the genome

what processes shorten DNA nearly 50 fold?

wrapping of DNa and arrangement of the nucleosomes to form the 30 nm fiber