Biology Unit 6 Exam Flashcards

What is the primary source of heritable information?

DNA and sometimes RNA

Prokaryotic organisms usually have what types of chromosomes? (shape and number)

single, circular

Eukaryotic organisms usually have what types of chromosomes? (shape and number)

multiple, linear

What are plasmids?

small, circular, double-stranded DNA molecules

Adenine pairs with…

thymine

Cytosine pairs with…

guanine

In RNA, adenine pairs with…

uracil

Which bases are purines?

Guanine and Adenine

Which bases are pyrimidines?

Cytosine and Thymine

Purines have what type of ringed structure?

double-ring

Pyrimidines have what type of ringed structure?

single-ring

DNA is synthesized in what direction?

5’ to 3’

Why is DNA replication a semi-conservative process?

one strand of DNA is conserved and used as a template strand

Which enzyme unwinds the DNA?

DNA helicase

What does topoisomerase do?

relaxes supercoiling in front of the replication fork

DNA polymerase requires what to initiate DNA synthesis?

RNA primers

DNA is synthesized discontinuously on which strand?

the lagging/discontinuous strand

What does ligase do?

joins okazaki fragments on the lagging strand

mRNA molecules carry information from DNA to where?

the ribosomes in the cytoplasm

what are the sequences on tRNA molecules that base pair with mRNA?

anti-codons

What modifications does the mRNA transcript go through?

-addition of a poly(A) tail

-addition of a GTP cap

-Removal of introns and splicing of exons

What is the process that results in different generated versions of the spliced mRNA molecule called?

alternative splicing

In prokaryotic organisms, which two processes involving DNA and mRNA are coupled? (meaning they happen at the same time)

transcription and translation (the mRNA molecule is translated as it’s being transcribed)

What are the three steps of translation?

initiation, elongation, and termination

When is translation initiated?

when the rRNA in the ribosome interacts with the mRNA at the start codon

What are the sequences of nucleotides on the mRNA that are read in triplets called?

codons

Each codon encodes a specific…

amino acid

Nearly all living organisms use the same genetic code, which is evidence for what?

common ancestry of all living things

Which direction does genetic information flow in retroviruses?

from RNA to DNA

Which enzyme copies the viral RNA genome into DNA?

reverse transcriptase

What do regulatory sequences do?

they interact with regulatory proteins to control transcription

What are epigenetic changes?

changes that affect gene expression through reversible modifications and histones

Why is cell differentiation important?

so that different cells do different jobs; it’s why you don’t have stomach cells in your brain or brain cells in your stomach

What is an inducible operon?

an operon that is usually off and can be turned on

What is a repressible operon?

an operon that is usually on and can be turned off

What do promoters do?

bind to initiate transcription

What do negative regulatory molecules do?

they inhibit gene expression by binding to DNA and blocking transcription

What is the primary source of genetic variation?

mutations

Down syndrome is also known as?

trisomy 21

what is transformation?

when bacteria take up free-floating DNA to use for themselves

What is conjugation?

cell-to-cell transfer of DNA

What is transposition?

the movement of DNA segments within and between DNA molecules

what is transduction?

viral transmission of genetic information

What does gel electrophoresis do?

it separates molecules according to size and charge

What is PCR?

polymerase chain reaction: amplifies DNA fragments

What are RNA nucleotides composed of?

a 5 carbon ribose sugar, a phosphate, and a nitrogenous base

Describe tRNA structure.

T-shaped, made of RNA nucleotides. They have amino acids attached at the top, and an anticodon attached at the bottom.

Describe tRNA function.

responsible for carrying the amino acids to the ribosome during translation and transferring them on to the growing polypeptide chain (amino acid) chain.

Describe mRNA structure.

a single stranded sequence of RNA nucleotides

Describe mRNA function.

carries the instructions for producing a specific protein from the nucleus to the ribosome

Describe rRNA structure.

sequence of RNA nucleotides that bind to ribosomal proteins in order to form the whole ribosome

Describe rRNA function.

assists with translation of messenger RNA

What are the three steps of cell signaling?

reception, transduction, response

What is the central dogma of biology?

DNA → RNA → Protein

During RNA splicing, what’s cut out and what’s kept?

introns are cut out and exons are kept

What is a silent mutation?

when a base change results in the same amino acid

What is a missense mutation?

when a base change results in a different amino acid

what is a nonsense mutation?

when a base change results in a STOP codon

insertions/deletions result in what?

frameshift mutations

Are operons found in eukaryotes or prokaryotes?

prokaryotes

What do operons allow prokaryotes to do?

turn genes on and off quickly in response to their environment

What are regulatory sequences?

stretches of DNA that interact with regulatory proteins to control transcription

Do regulatory sequences need to be close to the gene in order to regulate gene expression?

no, especially not in eukaryotes

What do epigenetics control?

which genes are physically available for transcription

What is methylation?

the addition of a methyl group

What is acetylation?

the addition of an acetyl group

Are methylation and acetylation patterns heritable from parent to offspring?

yes

What is microRNA?

small, non-coding sequences of RNA

Which protein produces miRNA?

the dicer protein

What happens when miRNA binds an mRNA transcript?

mRNA is degraded or translation is blocked - either way, gene expression is silenced

are viruses considered to be alive?

no

viruses must do what in order to reproduce?

infect a host cell

What is the protein shell that surrounds viral genetic information?

the capsid

What is the viral envelope?

the cell-membrane like structure made of lipids that surrounds the capsid

What is the spike protein in viruses?

spike shaped projections made of protein that help viruses attach to and infect their host cells

Viruses are (specific/unspecific)?

specific

prokaryotic viruses are also called..

bacteriophages or just phages

Retroviruses store their genetic material in what direction?

3’ to 5’

Which type of organisms do bacteriophages infect?

only prokaryotes

What is the lytic cycle?

the virus infects the host cell and uses host organelles to make more copies of itself

What is the lysogenic cycle?

the virus inserts its DNA into the host cell, and the DNA adds itself into the host cell DNA

what are restriction enzymes?

produced by the bacteria to break down phage DNA and prevent infection