Chapter 13: Mutation

Question 1

What are VNTRs? How are they used?

Answer 1

VARIABLE NUMBER TANDEM REPEATS:
Adjacent repeats of single or more nucleotides

• Large component of the non-coding DNA
• Often used in forensic DNA analysis as a genetic fingerprint given their variation in the genome

Question 2

What are RFLPs?

Answer 2

RESTRICTION FRAGMENT LENGTH POLYMORPHISMS:
Technique used to analyze variations in DNA sequences among individuals. A type of “genetic marker” that results from variations in DNA sequence recognized by restriction enzymes.

• Used for DNA fingerprinting
• They are found in VNTRs and then run on a gel

Question 3

What is the Pribnow Box?

Answer 3

A PROMOTER SEQUENCE IN PROKARYOTES (similar to TATA box in eukaryotes, it will only be Ts and As and will be 6-12 bp from the start codon)

Question 4

In which direction does transcription and translation occur?

Answer 4

Things are always built 5’ -> 3’ (because we can only add to 3’ OH)

• 5’ to 3’ is usually top strand and 3’ to 5’ is usually bottom strand

Question 5

How is the DNA different in Prokaryotic cells vs eukaryotic cells? How does this difference influence genes?

Answer 5

Prokaryotes:
- Significantly less DNA (circular and underwound)
- Supercoils of DNA form the looped Nucleoid of bacteria
- THE SIZE OF THE GENOME HAS NOTHING TO DO WITH ORGANISM COMPLEXITY

EUKARYOTES HAVE MORE NONCODING DNA.
- The more non-coding DNA, the more complex
- 98% of Human Genome doesn’t code for a protein
- Eukaryotes have many internal structures and an extensive lipid membrane (phospholipids)

Question 6

What are Histones? What happens without Histones?

Answer 6

PROTEINS that provide the structural support for chromosomes

• DNA becomes relaxed and spreads out (making a mess) without Histones

Question 7

Describe the following terms:

Nucleosomes
Chromatin
Heterochromatin
Euchromatin

Answer 7

Nucleosomes: DNA wrapped around Histone Proteins (like beads on a string)

Chromatin: Large amount of Nucleosomes wrapped together in a thicker (rope)

Heterochromatin: Large amount of Chromatin packed tightly together (like a closed book) and DNA is not easily accessible

Euchromatin: The less condensed and more loosely packed form of chromatin (like an open book) and DNA is easily accessible

Question 8

What is a genome? What determines the complexity of an organism?

Answer 8

The complete (haploid) set of genetic material -> ALL DNA

• There is no relation between complexity of an organism and the size of the genome or the number of genes: COMPLEXITY IS DETERMINED BY THE PROPORTION OF NONCODING DNA

Question 9

What 3 complications can arise when trying to sequence a genome?

Answer 9

1) Tandem Repeats
2) Dispersed Repeats
3) Simple-Sequence Repeats

Question 10

What are Sequence Motifs and why are they so important? Give some examples.

Answer 10

Nucleotide or amino-acid sequence PATTERNS that are widespread and usually assumed to be related to certain biological functions

• Helps Annotate The Genome!
• ex: TATA Box
• ex: Polyadenylation Signal
• ex: Shine-Dalgarno Sequence
• ex: Zinc Finger Sequences

Question 11

What is one huge possibility that comes from sequencing the entire human genome?

Answer 11

PERSONALIZED MEDICINE! Although everyone’s DNA is unique, the location of gene sites are very similar between all humans. Because of this, we can:
-> predict what diseases we’ll be susceptible to
-> understand individual drug sensitivities
-> provide the best treatment plans for each individual

Question 12

What are Introns and Exons? Why are they important?

Answer 12

Introns stay “in” the nucleus and Exons “ex”it the nucleus.

• Allow for the coding of hundreds of proteins from a single mRNA strand
• Furthers understanding of which portion of the genome corresponds to sequences in the mRNA

(Exons are used to make proteins. A huge part of sequencing is determining what parts of the DNA sequence make mRNA)

Question 13

What makes up the coding and non-coding DNA?
What is the difference between coding and non-coding DNA?

Answer 13

Coding DNA, MADE UP OF EXONS, contains instructions for building proteins—the molecular machines that carry out various functions in the cell.

Non-coding DNA (INCLUDES INTRONS) and does not provide direct instructions for building proteins. However, it plays crucial roles in the regulation and function of the genome.

Question 14

What happens to the ratio between noncoding and coding DNA as organisms become more advanced?

Answer 14

NON-CODING DNA BECOMES A LOT MORE PREVELANT AS ORGANISMS BECOME MORE ADVANCED

Question 15

How could we identify a polyploidy organism?

Answer 15

• Microscopic Examination
• DNA Content Measurement
• Chromosome Analysis
• Genetic Analysis
• PCR-Based Techniques
• Genomic Comparison

Question 16

What is disjunction?

Answer 16

Disjunction happens when homologous chromosomes move apart toward the opposite poles of the cell in anaphase I. Disjunction again occurs when sister chromatids separate and move away from each other during anaphase II.

Question 17

What is nondisjunction? What can it lead to?

Answer 17

Nondisjunction is the failure of a pair of chromosomes to separate during anaphase of cell division

• Often lethal
• In mitosis can lead to cancer
• In meiosis leads to Down Syndrome, Turner Syndrome, etc.

(nondisjunction is the leading cause of pregnancy loss and birth defects)

• The result is that one daughter cell receives an extra copy of one chromosome and the other daughter cell receives no copy of that chromosome

Question 18

What are the different genetic abnormalities that can occur from nondisjunction? Be able to distinguish between them.

Answer 18

Trisomy 21 (Down Syndrome)

Trisomy 18 (Edwards Syndrome)

Trisomy 13 (Patau Syndrome)

XXY, XYY, XXX, X
(females usually XX and males XY)

Question 19

What are the potential structures of the viral genome?

Answer 19

The genome of a virus may consist of DNA or RNA, which may be single stranded (ss) or double stranded (ds), linear or circular

Question 20

What makes the genomes of mitochondria and chloroplasts unique?

Answer 20

They have their own DNA!

These organelles are thought to have once been free-living bacterial cells that were engulfed by primitive eukaryotic cells.
Similar to prokaryotic cells, they have circular DNA

Question 21

How much of your genome is responsible for protein production?

Answer 21

Only about 1-2% of DNA is made up of protein-coding genes; the other 98-99% percent is noncoding.

Question 22

What does ploidy mean? How can you tell the difference between diploid and haploid?

Answer 22

Ploidy relates to the number of chromosome sets:
Haploid is having only 1 set (of 23) chromosomes and Diploid is having 2 sets (of 23 chromosomes in humans)

(polyploidy is having more than two sets of chromosomes)

Question 23

What is an Open Reading Frame?
What are some of the mutations that can change an open reading frame?

Answer 23

Long stretch of codons for amino acids with no stop codon

Can be mutated by Frameshift Mutations: deletions or additions of 1, 2, or 4 nucleotides that change the ribosome reading frame and cause premature termination of translation at a new nonsense or chain termination codon (TAA, TAG, and TGA).