exam 3 BIOL 1009

primary function of RNA

to help produce proteins

what are the monomers of nucleic acids called

nucleotides

what are the three parts of the nucleotide

a phosphate group, a sugar, and a nitrogenous base

what sugars are found in nucleotides

deoxyribose and ribose

what are the two categories of nitrogenous bases

purines and pyrimidines

are nucleotides hydrophobic or hydrophilic

hydrophilic

what type of reaction joins nucleotides together

a condensation(dehydration) reaction

what type of bond join nucleotides together

a phosphodiester bond

what forms the backbone of DNA and RNA

an alternating sugar-phosphate backbone

what is base pairing

hydrogen bonding between complementary nitrogenous bases

which DNA bases pair together

adenine with thymine

cytosine with guanine

what does it mean for two DNA strands to be complementary

every base on one strand pairs correctly with a base on the other strand

what do the 1’ -5’ numbers represent in DNA

the numbered carbon atoms in the sugar

which carbon are connected by a phosphodiester bond

the 3’ carbon of one sugar to the 5’ carbon of the next

what is found at the 5’ end of a DNA strand

a phosphate attached to the 5’ carbon

what is found at the 3’ end of a DNA strand

an exposed 3’ carbon on the sugar

what does antiparallel mean is DNA

one strand runs 5’>3’ while the other run 3’>5’

how is a DNA sequence written

using the one-letter abbreviations for the nitrogenous bases and indicating the 5’ and 3’ ends

what surrounds the nucleus

the nuclear envelope

what is the nuclear envelope

a double membrane surrounding the nucleau

what is the function of the nuclear lamina

it procides structural support and maintains the nucleus shape

what is the function of the nuclear pores

they regulate what enters and leaves the nucleus

what is the nucleolus

a dense region where ribosomes are assembled

what proteins organize DNA in the nucleus

histones

what is a chromatin

DNA wrapped around histone proteins

why does chromatin condense before cell division

to form chromosomes that can be separated accurately

what is a chromosome

a tightly condensed form of a chromatin visible during cell division

what are the two major functions of the cytoskeleton

it provides cell structure and allows movement within and of the cell

why is the cytoskeleton considered dynamic

its components constantly grow and shrink

how do motor proteins use the cytoskeleton

they move cargo along cytoskeletal tracks

what protein makes up microfilaments

actin

what is treadmilling

actin adds to one end of a microfilament while being removed from the other end

what is the main function of microfilaments

they help cells move and provide mechanical support

how do microfilaments move a cell

by growing against the cell membrane while shrinking at the opposite end

what protein makes up microtubules

tubulin

how do microtubules grow and shrink

they add and remove tubulin from the same end

where do microtubules orgininate

the centrosome

what structures in the centrosome help start new microtubules

centrioles

what is the primary function of microptubules

they act as tracks for motor proteins to transport cargo throughout the cell

compare DNA and RNA

DNA stores genetic information and contains deoxyribose, RNA helps make proteins and contains ribose

compare chromatin and chromosomes

chromatin is loosely packed DNA used during normal cell function

chromosomes are condensed chromatin before cell division

compare microfilamtents and microtubulues

Microfilaments are made of actin and mainly provide cell movement and support, while microtubules are made of tubulin and primarily transport cargo and form structures like the mitotic spindle.

compare histones and chromatin

histones are proteins that DNA wraps around

chromatin is the DNA histone complex

what is cell division

the process in which one parent cell divides to prosuce two genetically identical daughter cells

why do single celled organisms divide

to reproduce

who do multicellular orgnisms divide their cells

for growth, development, and tissue repair

what is G0

a resting state in which a cell is not actively preparing to divide

which cells divide most frequently

cells that expirence frequent wear and tear, such as skin and intestinal cells

what are the three stages of interphase

G1

S

G2

what happens during G1 of interphase

the cell grows and carries out normal functions

what happens during S phase

DNA is replicated

what happens during G2 phase

the cell grows more and prepares organelles for mitosis

why are cell cycle checkpoints important

they prevent damaged or abnormal cells from dividing

what does the G1 checkpoint check

growth factors, nutrients, internal signals, and DNA damage

what does the G2 checkpoint check

internal signals and DNA damage before mitosis begins

what happens if DNA damage is detected at a checkpoint

the cell cycle stops until the damage is repaired

why can failure of checkpoints lead to cancer

damaged cells continue dividing and accumulate mutations

why must DNA be replicated

so each daughter cell recieves a complete copy of the genome

where does DNA replication begin

at origins of replication

what is a replication fork

the y-shaped region where DNA is unwound and copied

what is a replication bubble

the opened region of DNA containing two replication forks

what is the function of helicase

unwinds the DNA double helix

what is the function of primase

synthesizes a short RNA primer

why is an RNA primer needed

DNA polymerase cannot start a new DNA strand on its own

what is the function of DNA polymerase

adds new DNA nucleotides to the growing strand

in which direction does DNA polymerase build DNA

It adds nucleotides only to the 3′ end, so the new strand grows 5′ → 3′.

how does DNA polymerase know which nucleotide to add

by following complementary base pairing rules

what is the function of ligase

joins DNA fragments together by sealing the sugar phosphate backbone

what is the leading strand

the DNA strand synthesized continuously

What is the lagging strand

The DNA strand synthesized in short segments

What are Okazaki fragments

Short DNA segments made on the lagging strand

Which enzymes are involved in making Okazaki fragments

Primase, DNA polymerase, and ligase

What is proofreading

DNA polymerase correcting mismatched bases during DNA replication

What is mismatch repair

Repair replication errors missed during proofreading

What is nucleotide excision repair

Removal and replacement of damaged DNA caused by environmental factors

What happens if DNA damage is not repaired before permanent

the mutation becomes permanent

How can DNA mutations affect proteins

They can change the amino acid sequence and altar protein function

What is a somatic mutation

A mutation in body cells that is not inherited

What is Germline mutation

A mutation in sperm or egg cells that can be inherited

What happens during telophase

The nucleus reforms, chromosomes decondense, and spindle fibers break down

What is cytokinesis

The physical division of the cytoplasm into two daughter cells

What is the central dogma of molecular biology

DNA→RNA→protein

What is transcription

Making RNA from DNA template

Where does transcription occur

In the nucleus

What is translation

Making a polypeptide(protein) from an RNA molecule

Where does translation occur

At ribosomes in the cytoplasm

What is transcription

The process of making an RNA copy of a gene from DNA

what is the purpose of transcription

to produce an RNA molecule that carries genetic information for protein synthesis

what base replaces thymine in RNA

uracil

what are the base pairing rules during transcription

G↔C, C↔G, T→A, A→U

what is the coding strand

the DNA strand that has the same sequence as the RNA (except T IS REPLACED BY U

what is the template strand

the DNA strand used by RNA polymerase to build the RNA transcript

what is a promoter

a DNA sequence upstream of a gene where transcription proteins

what is the TATA box

a promoter sequence in many eukaryotic genes where transcription proteins assemble

what do upstream and downstream mean

upstream is before the gene(toward the promoter)

downstream is after the gene

what is the function of transcription factors

they bind the promoter and recruit RNA polymerase

what enzyme perform transcription

RNA polymerase

what are the two main jobs of RNA polymerase

unwind DNA and synthesize RNA

what is the transcription initiation complex

RNA polymerase plus transcription factors assembled at the promoter

how does DNA methylation affect gene expressions

it decreases gene expression by reducing access to DNA