Genetics- Test 1

What is one of biology's unifying principles

All organisms use genetic systems that have a number of features in common

What is a genome

A complete set of genetic instructions for any organism

What makes a good genetic model?

• Short generation line

• Large but manageable number of progeny

• Adaptability to laboratory environment

• Ability to be housed and propagated inexpensively

What are the three chemical composition and structure of DNA and RNA

1. Pentose Sugar (anchor)

2. Nitrogenous Base (data)

3. Phosphate Group (linker)

What pentose sugar does DNA and RNA have

DNA - deoxyribose RNA - ribose

What nitrogenous bases do DNA and RNA use

DNA:

• Thymine

RNA:

• Uracil

What is the joining of the anchor and data

Base linked to sugar by 1' carbon of pentose sugar

• these are nucleotides

What is the linker

A phosphate group attached to the 5' Carbon

Covalent bonds between a phosphate group of one nucleotide and the 3' carbon of the next nucleotides sugar

Phosphodiester bonds

A --> T has how many H bonds

2

C --> G has how many H bonds

3

Watson and Crick investigated the structure of DNA not by collecting new data, but by ___________________________________ about the chemistry of DNA to construct molecular models

using all available information

DNA is a ______ helix

Double

The strands of DNA are

Antiparallel

_______ form between complementary base pairs

Hydrogen bonds

A single set of genes

1C value

T/F Haploid means DNA = 1C

True

N is used to represent what?

The number of chromosome molecules in a cell

T/F Most cells are 2N, 1C Haploid

True

DNA is ______ for compaction

Supercoiled

What does supercoiling rely on

Topoisomerases

DNA with a protein "scaffold"

Chromatin

How many types of histones are there

5

T/F Histones have a net positive charge, thus bind to positive charged DNA

False; bind to negatively charged DNA

____ is a linker between nucleosomes

H1

Stabilizes DNA to the histone so it does not slide off

H1

The ______ is the fundamental repeating unit of chromatin

nucleosome

Diploid eukaryotic cells have how many sets of chromosomes

2

Laying the chromosomes out in a picture is known as a

Karyotype

What are two types of chromatin

1. Euchromatin

2. Heterochromatin

This type of chromatin stains lightly and holds "active" genes

Euchromatin

This type of chromatin stains darkly and holds genetically inactive genes

Heterochromatin

What are the two types of Heterochromatin

1. Constitutive heterochromatin

2. Facultative heterochromatin

Involved in maintaining chromosome structure and includes centromeres and telomeres

Constitutive heterochromatin

Has the potential to become condensed

Facultative heterochromatin

___________ are used by the cell during cell division to make sure that each daughter cell gets a copy of each chromosome

Centromeres

Where are telomeres located?

The ends of the chromosomes

What is located at the ends of chromosomes that help to protect the ends of the chromosomes from being degraded

Telomere

Adds new copies of the repeat so that the chromosome isn't destroyed by the loss of material after each round of synthesis

Telomerase

Hundreds to thousands of copies per cell

Circular genome

Replicative segregation can lead to both _______ and _________ cells

heteroplasmic and homoplasmic

T/F Each chromosome consists of linear, unbroken, double stranded DNA molecule (one or two, depending on mitosis/meiosis state)

True

DNA replication occurs by a __________________ mechanism

semiconservative

One double helix is unchanged by the process, the other is completely new

Conservative

Each strand is a mix of old and new DNA

Dispersive

One strand of double helix is conserved, the other is new

Semi-conservative

____________ catalyzes the formation of phosphodiester bonds

DNA polymerase

Recall that replication is always

5' --> 3'

DNA synthesis is _______ on one template strand of DNA and ____________ on the other

continuous; discontinuous

What are the 5 key elements of each replication fork

1. Helicase to unwind the DNA

2. SSBP to protect ssDNA

3. Gyrase to remove strain ahead of fork

4. Primase to synthesize RNA primer

5. DNA polymerase

DNA replication in Eukaryotes is initiated by ___________

RNA primers

DNA replication in eukaryotes is ______

semiconservative

What are the steps of packaging newly replicated DNA

1. histones must first disassemble to allow DNA synthesis

2. synthesis of new histones is coordinated with DNA synthesis

3. Then must reassemble on two new chromosomes

Main polymerases have a 3' --> 5' __________ activity

exonuclease

DNA replication is _______

semi-conservative

T/F A small number of enzymes are involved in DNA replication

False; Large

G1 contains the ________. Once the cell passes this point, then it must enter S phase

'checkpoint'

What happens during the S phase

DNA untwists and replicates

What are the 5 phases of Cell life-cycle

1. G1

2. G0

3. S

4. G2

Formation of two cells from one cell

Mitosis

How many stages are in mitosis and what are they

5 stages:

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

What happens during prophase of mitosis

• Chromosomes condense

• Two sister chromatids become detectable

• Mitotic spindle assembles outside the nucleus

What happens in metaphase?

• Chromosomes arrange on metaphase plate

• Centrosomes at opposite poles

• Microtubules from centrosomes to kinetochore

What happens during anaphase?

• Sister chromatids separate

• Chromosomes move toward opposite poles

What happens during telophase?

• Sister chromatids arrive at opposite poles (now called chromosomes)

• Nuclear membranes form

• Chromosomes relax and lengthen

T/F Meiosis includes four cell divisions

False

Chromosomes cross-over (recombination) during what stage of Meiosis

Prophase I

Random distribution of chromosomes in meiosis produces ________

genetic variation

What is the Central dogma?

DNA-transcription-RNA-translation-protein

What is the first step of the central dogma

Transfer of genetic material from DNA to mRNA (get the info out of storage)

Describe mRNA

• Has instructions to make a protein

• Each protein has a unique mRNA

Describe tRNA

Translates instructions into protein "language"

Describe rRNA

Machine that "builds" a protein

What are the key components needed for transcription

1. A DNA template

2. The raw materials (ribonucleotide triphosphates) needed to build a new RNA molecule

3. The transcription apparatus, consisting of the proteins necessary for the catalyzing the synthesis of RNA

What are 3 main types of RNA polymerases

1. RNA Pol I

2. RNA Pol II

3. RNA Pol III

What does RNA Pol I do

Transcribes ribosomal RNA (rRNA)

What does RNA Pol II do

Transcribes pre-messenger mRNA

What does RNA Pol III do

Transcribes tRNA (and other small RNAs)

Describe what a promotor is

Sequence that transcription machinery recognizes and binds (generally not transcribed)

Describe Coding region

The sequence that is copied (transcribed) from DNA to RNA

Define terminator

Specific sequences that indicate transcription should stop (generally is transcribed)

Describe a core promotor

• Generally required for any transcription

• Transcription factors and regulatory factors can bind here (control expression timing)

• TATA box

Describe a regulatory promoter

• Variety of consensus sequences

• Transcription factors and regulatory factors can bind here

• Affect the rate of transcription

• Directly or indirectly make contact with basal transcription machinery

Distal locations can also enhance transcription

Enhancers

What is initiation of protein coding genes

If the promotor (core and regulatory) and enhancers "say so", a protein-coding gene is transcribed

Keep adding nucleotides

Elongation

For RNA Pol II there is no specific termination sequence

Termination

• can continue for 100s - 1000s bp

What is a gene

Gene is the fundamental unit of heredity

Most eukaryote organisms have ________

intons

What is an exon

Region of DNA that codes for a protein

T/F In eukaryotes, intron size and number is related to organism complexity

True