Genetics Exam 1 (Intro + DNA structure)

Lectures

What is the chromosomal theory of inheritance

Genes for phenotypic traits are carried on chromosomes

What is mutagenesis

Describes how chromosome can be altered by mutation

Gene

section of DNA that codes for a gene product

Variant

A stretch (does NOT have to be gene) of DNA w/ different sequences among individuals.

Allele

a specific gene variant

Coding genetic material

Gene

Noncoding genetic material

DNA

Genome

All coding (aka genes) and noncoding genetic material (DNA) of an organism

Human genome

wild-type arrangement/sequence (reference)

Individual genome

Considers specific alleles (variants)

What are the 5 subdisciplines of Genetics?

Transmission Genetics

Molecular Genetics

Genomics

Population Genetics

Quantitative Genetics

Transmission Genetics

Mendelian, classical

• how traits are passed down from parents to offspring

• monogenetic, discrete, life vs. death, sex-linked, dom/rec, autosomal

  ex) peas, fruit flies

Molecular Genetics

Structure and function of genes

How expression of genes work

Genomics

The analysis of all genetic material from organisms(s) or species

Population Genetics

Study of traits determined by one or a few genes in a group of individuals

ex) determining the frequency of disease like Cystic fibrosis

Quantitative Genetics

Study of polygenic traits + environmental influences on phenotypic ex) crop yield, behavioral, how well yeast ferments

What are the 4 functions of genetic material

1. Must contain, in stable form, information about an organism’s cell structure, function, development, and reproduction

2. Must be able to be expressed so the information can be used for the above functions

3. Must replicate accurately so progeny cells have the same information as parent cells

4. Must be capable of change because without change, a population would not have variation. Adaption and evolution would not occur.

DNA

deoxyribonucleic acid

RNA

ribonucleic acid

All known prok, euk, and a few viruses have _____ as the genetic material

dsDNA

Many viruses have ___ as their genetic material

RNA

Who published the DNA structure in 1953 and won Nobel prize in 1962

Watson and Crick

What were the 4 influences in which the molecular structure of DNA was based on

1. Polymer of nucleotides containing five-carbon sugar (ribose), base, and phosphate group

2. Chargaff’s rule

3. Rosalind Franklin’s X-ray diffraction data

4. Their knowledge of chemistry (bonding potentials, bond lengths/angles. repulsive forces, etc.)

What gives DNA (and RNA) a net negative charge and is the reason DNA is a nucleic acid

phosphate group

Where is the phosphate group attached to ribose?

phosphodiester bond, 5’ carbon/3’

Where is the nucleotide base attached ribose?

glycosidic bond, 1’ carbon

If OH is attached on 2’ carbon, then it is ___

RNA

Base pairing allows DNA replication to be _____

semiconservative

What is Chargaff’s rule

A:T = 1

G:C = 1

Total amount of total AT and GC can differ

Purines (A+G) and Pyrimidines (T+C) are the same

What are the 2 things that Franklin and Wilkins conclude about DNA

1. Helical structure

2. Distinct periodicities along the helix

   • 3.4 nm = 360 turn

   • 0.34 nm = spaces between bases

   • About 10 base pairs per turn

Franklin and Wilkins’ Distinct periodicities along the helix

• 3.4 nm = 360 turn

• 0.34 nm = spaces between bases

• About 10 base pairs per turn

What are nucleotides subunit connected by

phosphodiester bonds

What are the 5 characteristics of B-DNA

1.) Sugar-phosphate —> phosphodiester backbone (outside)

2.) Bases on inside, held together by H-bonds and are complementary

3.) dsDNA consists of two polymers that would in Right-handed helix

4.) Major and minor groove

5.) Antiparallel, one 3’ to 5’ and one 5’ to 3’

Why does B-DNA have a major and minor groove

Angles of glycosidic bonds, proteins recognize the sizes of the grooves and molecular interactions like H bonding potentials

What is directionality referred to

polarity, model of DNA as two strands of opposite directionality

How much is each nucleotide is twisted relative to the adjacent nucleotide

36 degrees

DNA vs. RNA (3 characteristics each)

DNA:

• Has H on 2’ carbon

• Thymine

• Is genetic material for ALL known prok and euk

RNA:

• Has OH on 2’ carbon

• Uracil

• Is genetic material for SOME viruses

Structure of RNA (6)

1.) Single stranded

2.) some based are modified

3.) never “naked” —> structures are recognized by specific proteins

4.) folded structure, based upon sequences —> complementary based pairs allow for sequence-dependent secondary structures including helical structures (hairpins)

5.) Coated with associated protein

6.) Secondary structure and protein interaction are important —> recognition of mRNA and ncRNA (noncoding) RNA function

Any molecule that serves as the genetic material must have the following characteristics (3)

• ability to be replicated

• ability to store information

• the potential to be changed via mutation

Why doesn’t genetic material HAVE to have the ability to directly influences the development of traits (2)

There can be other factors that can influence traits

1. Environmental

2. Polygenic complex traits

Polygenic Complex Traits

Multiple genes influence the same trait

Hack for “(A+G) = (C+T)” type of questions

Just eliminate A and T or C and G from both sides, whatever still stays is not valid with Chargaff’s rules.

How can you conclude genetic material is DNA from its nucleic acid analysis (ratio of A, G, T, C, U)

If it contains Thymine

How can you conclude genetic material is RNA from its nucleic acid analysis (ratio of A, G, T, C, U)

If it contains Uracil

How can you conclude genetic material is DOUBLE STRANDED from its nucleic acid analysis (ratio of A, G, T, C, U)

If its ratio of purine and pyrimidines is 1

How can you conclude genetic material is SINGLE STRANDED from its nucleic acid analysis (ratio of A, G, T, C, U)

If its ratio of purine and pyrimidines is NOT 1

Tm = Melting Point (aka when 1/2 material single strands) of a dsDNA is influenced by (3)

• Length of DNA

• GC content of sequence

• Total number of H bond between the base pairs

Why is GC stronger than AT?

GC has 3 H bonds

AT has 2 H bonds

What is ‘2+4 Rule of Thumb’

2(A+T) + 4(G+C) = Tm degrees Celsius

Each 360 degree turn of a double helix contains how many base pairs

10 (10.5) base pairs

Each 360 degree turn of a double helix contains how many nucleotides

20 (1 BP = 2 nucleotides)

What will two nucleic acid fragments do if they are complementary and antiparallel

spontaneously hybridize