Buhller genetics

Question 1

Pro- vs Eukaryotes

Answer 1

Prokaryote:

• Contains DNA in CIRCULAR strand
• Have FEW RIBOSOMES
• Does NOT contain a NUCLEUS
• NO NUCLEAR MEMBRANE
• Has CELL WALL
• Uni-cellular organisms

Eukaryotes:

• Contains DNA in LINEAR strands
• Have ,MANY RIBOSOMES
• Contains a NUCLEUS
• Has nuclear membrane
• Does NOT have CELL WALL
• Multi-cellular organisms

Question 2

T/F: Eukaryotic DNA is in direct contact with the cytoplasm

Answer 2

FALSE. THis is true for prokaryotes

Question 3

Why are eukarotic cells more susceptible to damage compared to prokaryotes?

Answer 3

Because they lack a cell wall

Question 4

Exaplin what happens when you inject mice with smooth (S) or rough (R) colonies of streptococcus pneumoniae

Answer 4

• if injected with S type, they die. But not if injected with R type. They also do not die if S type is boiled prior to injection
• If mice are injected with boiled S type plus live R type, mice die.

This suggests that DNA from S type passed the info to R type to make them virulent.

It was the PROTEIN that caused death. The code on the S type was still viable, therefore PROTEINS ARE THE FUNCTIONAL MOLECULES OF ORGANISMS

Question 5

What is the need for a nucleus

Answer 5

to protect DNA from the components of the cytoskeleton and other cellular objects during cell movement

Question 6

Define isoforms

Answer 6

Isoforms are proteins with similar functions and similar (but not identical) amino acid sequences

Question 7

Human cell contains __ chromosomes

Answer 7

46

Question 8

22 pairs of chromosomes are called ___. The other two are ___ chromosomes

Answer 8

22 pairs of chromosomes are called AUTOSOMES. The other two are SEX chromosomes

Question 9

chromosomes are classified on the basis of what?

Answer 9

the location of centromere

Question 10

Functions of chromosomes

Answer 10

• contain genetic material
• replicate
• segregate two copies of DNA during mitosis
• Maintain themselves between cell generations

Question 11

What is the DNA replication sequence?

Answer 11

The region where DNA double helix separates for duplication

Question 12

What is the centromere sequence?

Answer 12

region required for attachment of DNA molecules to mitotic spindle and to kinetochore proteins

Question 13

What happens are telomeres shrink?

Answer 13

the ability to duplicate decreases

Question 14

replication forks originate at a ___ __ in both mammalian and bacterial cells

Answer 14

REPLICATION BUBBLE.
This is a region where two DNA strands have separated.
Usually formed at replication origin sequences.

Question 15

DNA + protein =

Answer 15

chromatin

Question 16

2 types of chromatin

Answer 16

• Euchromatin: not condensed and not ready for reading

- Heterochromatin: appears as mass and is along the inner nuclear membrane

Question 17

Heterochromatin is divided further into two categories

Answer 17

1. facultative: may uncoil and be read

2. constitutive: never uncoils and is not read

Question 18

Major protein associated with DNA?

Answer 18

histones

Question 19

5 types of histones:

Answer 19

H1, H2A, H2B, H3, HA

Question 20

histones contain large numbers of what two amino acids? why is this significant?

Answer 20

Histones contain Lys and Arg. These are positively charged, which bind to negatively charged phosphate groups on DNA

Question 21

Nucleosome histones

Answer 21

• H2A, H2B, H3, and H4
• amino acids
• responsible for coiling DNA into nuclesomes
• 2 copies of each nucleosome

Question 22

Neuron nd lymphocyte contain the same complement DNA. What does this confirm

Answer 22

This confirms that different cell types in an organism contain the same complement of DNA, but each cell only “reads” the sequence which pertains to its function

Question 23

a fully differentiated skin cell was taken from a frog. What happened?

Answer 23

The nucleus of the skin cell was taken and implanted into an egg. The egg developed into a tadpole, which did not survive to adulthood.
This study proved that all cells except B cells in the body contain identical DNA which has the capacity to give rise to new offspring.
However, there are other factors involved that result in development of the mature functional organism

Question 24

a typical cell contains __ different classes of mRNA that code for proteins:

Answer 24

THREE different classes of mRNA that code for proteins:

1. abundant class
2. intermediate class
3. scarce class

Question 25

Which mRNA class is likely responsible for generating cell diversity?

Answer 25

mRNAs in the scarce class

Question 26

define gene

Answer 26

a region of DNA that produces a functional RNA molecule (mRNA)

Question 27

T/F: 100% of genes are unique in prokaryotes (ie. only one copy in the genome)

Answer 27

True. In eukaryotes only 64% are unique

Question 28

Genes in eukaryotic organisms have been divided into two broad categories:

Answer 28

1. Housekeeping genes: encode for proteins essential for cell viability (expressed in most cells) 2. Tissue-specific genes: encode proteins required for selected cells (eg. hemoglobin in RBCs, immunoglobulins in B cells)

Question 29

Explain the lac operon in E. coli as an example of the effect of nutrient availability on gene expression

Answer 29

E. coli grown in glucose + lactose uses glucose first. To use lactose, it must degrade glucose+galactose by B-galactosidase, which is not normally produced in E. coli. BACTERIAL GROWTH STOPS TO PRODUCE B-GALACTOSIDASE. -a repressor protein is bound to the promoter region ustream of lac operon inhibiting expression of the B-galactosidase gene -lactose is converted to allolactose -allolactose binds to the repressor protein and removes it from the promoter region -B-galactosidase is now synthesized.

Question 30

define epigenetics

Answer 30

A stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence

Question 31

Describe DNA methylation

Answer 31

- Part of epigenetics - mammalian genomes have CpG islands - methyl grouops resulting from methylation of cytosine stick out into the major groove of DNA and block binding of transcription factors to DNA and INHIBITING GENE EXPRESSION

Question 32

DNA methylation patterns can be altered by persisten ____

Answer 32

Inflammation

Question 33

Describe histone modification

Answer 33

Part of epigenetics - ACETYLATION promotes a more relaxed chromatin structure ALLOWING TRANSCRIPTION to occur - DEACETYLATION converts the chromatin into condensed form and REPRESSES TRANSCRIPTION

Question 34

What can be observed in chronic periodontitis with relation to epigenetics?

Answer 34

changes of DNA methylation patters and cytokine gene expression

Question 35

What has been reported concerning histone modification in dental pulp cells?

Answer 35

Histone modifications may induce differentiation and mineralization in dental pulp cells and these modifications play a crusial role in gene expression regulation and may promote pup repair and regeneration

Question 36

What can non-coding RNAs do?

Answer 36

they can bind to an mRNA molecule and cause its degradation or cause translational repression of the target mRNA. NON CODING RNAs PLAY AN ESSENTIAL ROLE IN ODONTOBLAST DIFFERENTIATION

Question 37

What percentage of the human genome is made up of transposable elements? what are transposons?

Answer 37

40%. Transposons are DNA sequenecs which can change positions within a genome. They can move in and out of chromosomes and cause a variety of short additions/deletions of nucleotide sequences. This results in the alteration of expression of nearby genes and effects various aspects of animal development and/or GENE EXPRESSION