Bio Sem 2 Unit 2 - Topic 1: DNA Structure & Gene Expression Revision

Question 1

Define Chromosome

Answer 1

Double-stranded DNA, a threadlike structure of nucleic acids and protein found in the nucleus of eukaryotic cells, carries genetic information in the form of genes.

Question 2

Define DNA

Answer 2

Carries the genetic info for the development and functioning of an organism

Question 2

Define genes

Answer 2

The basic unit of heredity (offspring) passed from parent to child.

Question 3

Parts that make up the DNA

Answer 3

Phosphate
Deoxyribose sugar
Nitrogenous base

Question 4

Define aneuploidy

Answer 4

The occurrence of one or more extra or missing chromosomes in a cell or organism

Question 5

Define polyploidy

Answer 5

A full extra set of chromosomes

Question 6

Compare the structure of DNA and RNA molecules

Answer 6

DNA -
Double-stranded, forms a double helix
Deoxyribose
Thymine
DNA is longer than RNA

RNA -
Single-stranded,
Ribose
Uracil
RNA varies in size but is usually shorter than the DNA they were copied from

Question 7

Compare the function of DNA and RNA molecules

Answer 7

DNA is responsible for storing and transferring genetic information

RNA directly codes for amino acids and acts as a messenger between DNA and ribosomes to make proteins.

Question 8

Describe the process of transcription including the main events and structures involved

Answer 8

• RNA polymerase binds to the promoter region of DNA
  and travels along unwinding sections, exposing the
  bases.
• RNA polymerase joins RNA nucleotides in a chain,
  complementary to the template strand of DNA, using
  Uracil instead of Thymine.
• RNA polymerase travels along the DNA until it reaches
  the termination sequence.

Question 9

Differentiate between introns and exons

Answer 9

An intron refers to non-coding sequences found in DNA or RNA. Exons refer to the coding portions of DNA or RNA.

Question 10

Describe the process of RNA editing

Answer 10

Pre-mRNA contains introns (noncoding sequences) and exons (codes for amino acids)

Introns are cut out, exons joined together to form the mature mRNA molecule

Question 11

Describe the process of translation including the main events and molecules involved

Answer 11

• Occurs at ribosomes (either free or attached to ER).
• mRNA molecule has the instructions for which amino
  acid is added to the polypeptide chain. The codon (3
  base sequence) on the mRNA signals which amino acid
  is needed.
• Transfer RNA molecules (tRNA) carry specific amino
  acids to the ribosomes

Question 12

Transcribe DNA template strand to mRNA strand -
TAC-GGA-CAT-ACG-TCG-ATC

Answer 12

AUG-CCU-GUA-UGC-AGC-UAG

Question 13

Determine an amino acid sequence from a mRNA -
AUG-CCU-GUA-UGC-AGC-UAG

Answer 13

Met-Pro-Val-Cys-Ser-UAG(stop)

Question 14

How are genes regulated in prokaryotes and eukaryotes?

Answer 14

Prokaryotes - The regulation of gene expression in prokaryotic cells occurs at the transcriptional level. There are three ways to control the transcription of an operon: repressive control, activator control, and inducible control.

Eukaryotes - Gene expression in eukaryotic cells is regulated by repressors as well as by transcriptional activators. Like their prokaryotic counterparts, eukaryotic repressors bind to specific DNA sequences and inhibit transcription.

Question 15

What will occur in the lac operon in the presence and absence of lactose?

Answer 15

Presence - In the presence of lactose, the lac repressor is released from the operator because the lactose has bonded to the repressor and transcription proceeds at a slow rate

Absence - In the absence of lactose, the lac repressor binds the operator, and transcription is blocked

Question 16

GUYS REMEMBER RNA POLYMERASE IS INSIDE THE NUCLEUS PRETTY SURE
AND THE RIBOSOME IS IN OR AROUND THE ROUGH ER, RNA POLY IS TRANSCRIPTION AND RIBOSOME IS TRANSLATION

Answer 16

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