Chapter 10

Question 1

Chromosomes

Answer 1

The structures within living cells that contain the genetic material

Question 2

Genome

Answer 2

The entire complement of genetic material in an organism or species

• bacteria’s genome is typically a singular circular chromosome
• eukaryotes genetic material is found in different cellular compartments, also have a mitochondrial genome, plants have chloroplast genome
• nuclear genome is one haploid set of chromosomes that resides in the cell nucleus.
• humans have 22 autosomes, The X & Y chromosome

Question 3

Protein-encoding genes

Answer 3

Account for the majority of bacterial DNA

Question 4

Intergenic regions

Answer 4

The nontranscribed regions of DNA located between adjacent genes

Question 5

Origin of replication

Answer 5

A sequence that is a few hundred nucleotides in length, functions as an initiation site for the assembly of several proteins required for DNA replication

Question 6

Repetitive sequences

Answer 6

May play a role in a variety of genetic processes, including DNA folding, DNA replication, gene regulation, and genetic recombination

*some are transposable elements that can move throughout the genome

Question 7

Microdomains

Answer 7

Loops that emanate from the core of bacterial chromosomes

Typically 10,000 base pairs in length

Length: Changes in response to environment

Question 8

Nucleoid-associated proteins (NAPs)

Answer 8

DNA binding proteins that micro/macro domains use to facilitate chromosome compaction and organization

*also facilitate chromosome segregation and gene regulation

Question 9

Structural maintenance chromosomes (SMC) proteins

Answer 9

Tether segments of DNA together

Question 10

Negative supercoiling

Answer 10

Happens due to an unwinding force on DNA

• makes chromosome much more compact, decreasing size
• Affects DNA function
• creates tension which is released by DNA strand separation in small regions
• strand separation promotes replication and transcription

Question 11

Topoisomerase I

Answer 11

Enzyme that relaxes negative supercoils

Question 12

Introns

Answer 12

Noncoding intervening sequences, That can greatly increase the length of eukaryotic genes

Size: from 100bp to 10,000+bp

Question 13

Exons

Answer 13

Regions of an RNA molecule that can remain after splicing has removed the introns

Question 14

Origins of replication

Answer 14

Chromosomal sites necessary to to initiate DNA replication

Question 15

Centromeres

Answer 15

Regions that play a role in the proper segregation of chromosomes during mitosis and meiosis, and is the site of kinetochores

-each eukaryote has 1 centromere usually at a constricted region of a mitotic chromosome

Question 16

Kinetochore

Answer 16

Assemble just before and during the very early stages of mitosis and meiosis; composes of a group of proteins that link the Centromere to the spindle apparatus during mitosis and Milos is, ensuring proper segregation of chromosomes to each daughter cell

Question 17

Telomeres

Answer 17

Serve several important functions in the replication instability of chromosomes

• prevent chromosomal rearrangements
• prevent chromosome shortening in two ways

Question 18

How telomeres prevent chromosome shortening

Answer 18

First, the telomeres protect chromosomes from digestion via enzymes called exonucleases that recognize the ends of DNA

Second, and unusual form of DNA replication occurs at the telomere to ensure that eukaryotic chromosomes do not become shortened with each round of DNA replication

Question 19

Sequence complexity

Answer 19

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

Question 20

Moderately repetitive sequences

Answer 20

Few hundred to several thousand times in genome

May play a role in the regulation of gene transcription and translation

Question 21

Transposable elements (TEs)

Answer 21

Short segments of DNA that have the ability to move within a genome, this is also where moderately repetitive sequences that do not play a functional role derive

Question 22

Highly repetitive sequences

Answer 22

Found tens of thousands or even millions of times throughout a genome

-relatively short

Question 23

Tandem arrays

Answer 23

This is where some moderately and highly repetitive sequences are clustered together, very short nucleotide sequence is repeated many times in a row

Question 24

Nucleosome

Answer 24

The repeating structural unit within eukaryotic chromatin, A double-stranded segment of DNA wrapped around a octamer of histone proteins

Question 25

The core Histone proteins

Answer 25

The octamer of histones contains two molecules each of four different histone proteins: H2A,H2B,H3,and H4) H1: found in most eukaryotic cells and is called the linker histone, tightly bounded * non-histone proteins bound to the H1 protein Play a role in the organization, compaction of chromosomes, and maybe nearby genes

Question 26

The 30nm fiber

Answer 26

This fiber sure is the total length of DNA another sevenfold. The confirmation of DNA Maybe substantially altered when this fiber is extracted from living cells Solenoid model: helical structure Zig zag model: advocated by Rachel Horowitz, Christopher Woodcock, used cryoelectron microscopy 3D Zig zag model: Timothy Richmond, highly favorable

Question 27

Nuclear matrix

Answer 27

Filamentous a network of proteins in the nucleus Parts: - Nuclear lamina: A collection of filaments that line the inner nuclear membrane - Internal nuclear matrix: It’s role is hypothesized to be an intricate find network of a regular protein filaments with many other proteins down to them.

Question 28

Matrix attachment regions

Answer 28

The MARs bind to specific proteins in the nuclear matrix, forming chromosomal loops

Question 29

Constitutive heterochromatin

Answer 29

Chromosomal regions that are always heterochromatic and permanently and active with regard to transcription

Question 30

Facultative heterochromatin

Answer 30

Chromatin that can occasionally enter convert between heterochromatin and euchromatin

Question 31

Condensin and Cohesin

Answer 31

Play a critical role in chromosomal condensation and sister chromatid alignment, both contain SMC proteins Condensin: found outside of nucleus, multiple condensin proteins bring chromatin loops closer together and hold them in place Cohesin: promotes the binding between sister chromatids, at anaphase, the Cohesins Down to the centromere are rapidly degraded by protease to allow sister chromatids separate