Exam 1 Molecular Biology Dr. Borgon

Watson and Crick published a paper called

"Molecular Structure of Nucleic Acids: A Structure for Deoxyribose Nucleic Acid"

The field of molecular biology started with the discovery of

DNA structure

Who felt that students weren't listening when he lectured, and were instead taking notes

watson

Who was born in 1822, became a monk, from Austria, and began making pe plant hybrids and studies the transmission of heredity?

gregor mendel

Who is infamous for the pea plants?

Gregor Mendel

What was the ratio that Gregor Mendel believed in?

9:3:3:1

Mendel selected ______ traits, which all happened to be on different chromosomes, and he kept detailed notes of at least __________ plant crosses

7; 29,000

Alleles

Alternate forms of a gene pair that control a characteristic

Homozygous

RR, rr, YY, yy

Heterozygous

Rr, Yy

Diploid

2n = 46 chromosomes in humans

Haploid

N = 23 chromosomes in humans

Segregation

Separation of two alleles

Independent assortment

Independent sorting of two different traits

Haploid is also known as a

Gamete

The basic rules of heredity were proposed in a paper by Mendel called

"Experiment in Plant Hybridization"

Genetic crosses between F1 generation produce

F2 generation

Pea plant seeds are _______ (dominant/R) or _________ (recessive/r)

Roud; wrinkled

What are the two alleles of the pea plants?

Round (R) and wrinkled (r)

Round seeds have a

Starch branching enzyme which was lost

T/F: gametes produce at random

true

Each F1 parent produces how many gametes?

Two (R or r)

Gametes combine to produce

F2

F2 has a __ phenotypic ratio and a _____ genotypic ratio

3:1 and 1:2:1

Inheritance is controlled by

Factors

Factors occur in ________, and alleles are ________ pairs of a gene pair

Pairs; alternative

When crossing peas with two traits, the F2 has a _:_:_:_ phenotypic ratio

9:3:3:1

Since the F2 offspring are not identical to the F1 generation, the traits must assort

independently

Yellow seeds have an enzyme ___________ to break down chlorophyll

SGR, or stay-green

There were three discoveries fromMendel's Law:

Law of Segregation (1st Law)

Law of Independent Assortment (2nd Law)

Principle of Dominance

Law of Segregation define

Genes occur in pairs and at the time of gamete formation, one of each pair enters the gametes. Half the genes carry one allele, the other half the other allele.

Law of Independent Assortment define

Genes for different traits assort independently of one another in the formation of genes

What is an example of Independent Assortment?

One gener pair Rr sorts independent of another gene pair Yy when RrYy produce gametes

Principle of Dominance

Some alleles are dominant while others are recessive, and an organism with at least one dominant allele have the dominant phenotype

Incomplete dominance

Some alleles show a blend of traits that is intermediate between the two; neither dominant nor recessive

With incomplete dominance you can get a _____ ratio

1:2:1

What is an example of incomplete dominance

i.e.mixing red and white makes pink in snapdragons

snapdragon make a red pigment called

Anthocyanin

If you cross pink and a white you can't get a red but you can cross ______ and a ______ to get a red

Pink and pink

Sickle cell anemia is

Incomplete dominance because of the intermediate phenotype

Sickle cell trait is

Codominance

Codominance define

Neither allele is dominant over the other, both are expressed and result in a phenotype

Traits do not mix

No intermediate phenotype

Many genes are involved such as ________, which crosslinks ________ in the root to give hair strength

Trichohyalin

T/F: blood types are not codominance

False; they are codominance

Blood types are determined by three alleles

A, B, and O

Blood Type A and B encode different

Glycosyltransferases

Blood Type O has no

Enzyme

A and B are ___________, resulting in an Ab blood type. Both are _______ over O

Codominant; dominant

Define epistasis

When one gene modifies another

Dog coat color is determined by two different genes:

Dark pigment (eumelanin, B) ude to a protein tyrosinase-related protein 1 (TRYP1)

Expression in hair (expression, E) is epistatic, due to melanocortin 1 receptor (MCR1)

Dogs that have both B and E are

black

Dogs that have recessive b and dominant E are

brown

Dogs that have recessive ee are ________ regardless of the B/b alleles

yellow

The _______ allele produces an enzyme with very high activity, which in turn produces a large amount of brown pigment

ebony

The _____________ allele produces only a low amount of brown pigment

swedish-blonde

Many traits are

Polygenic and are controlled by two or more genes

Who described chromatin and mitosis?

Walther Flemming

Who brought together cytology and genetics?

Walter Sutton

What did Walter Sutton observe?

He observed that diploid cells consist of two sets of chromosome sand during meiosis each gamete receives only one chromosome of each homologous pair

Mitosis

Produces identical daughter cell (2n → 2n)

Meiosis

Produce gametes (2n → n)

Genes show independent assortment if either of two conditions are met

The genes are located on separate chromosomes

The genes are far apart on the same chromosome

Who used fruit flies are model organisms?

Thomas Hunt Morgan

What is the scientific name for a fruit fly?

Drosophila melanogaster

What did Thomas Hunt Morgan say about Mendel's result?

Thomas Hunt Morgan didn't believe Mendel's results; he believed that species were created instantly by mutations

Who discovered crossing-over in salamander?

Frans janssens

What did Frans Janssenns call this discovery of crossing-over in salamanders?

Chiasmata

What did Frans Jenssen conclude?

What he concluded was that chromosomes cross-over and sometimes when they cross-over they switch segments/parts

If parents AABB x aabb are crossed then F1 will be

AaBb

In crossing over, since F1 gametes are now AB and ab, then F2 will have a

3:1 phenotypic ratio

From this crossing-over you may get ___% parental and ____% new combination from crossing over, with offspring having one dominant and one recessive traits

70% and 30%

When and by who was crossing over actually proven correct?

In 1931 by Barbara McClintock and Harriet Creighton

What did Barbara McClintocka nd Harriet Creighton use to cross over?

corn

What did they notice from the corn's chromosome that was different?

They noticed that one chromosome was marked by compacted regions that formed knob-like structures and extra chromosomal material

What can only appear as a result of crossing over?

The recessive phenotype

How does each pair of chromosomes always manage to cross over at least once?

Cross-linking is a requirement for meiosis

Why is the recombination greater in females vs males?

Females have about a 20% greater recombination than males

Crossing over is a tool for determining the...

distance between two genes or loci, which is one way to locate the relative positions of genes on chromosomes

What is the percentage of linkage?

50%-100%

What is the percentage of crossing over recombinants?

0%-50%

The farther apart two genes are on a chromosome...

The greater the chance of crossing over

At 50% genes assort independently and show

50% linkage

1% of recombination/crossing-over is equal to

1 cM (centimorgan)

A single, triple, or any odd number of crossovers between two traits produces a

Recombinant offspring

A double crossover (or any even number) between two traits restores the original phenotype, resulting in a

Nonrecombinant offspring

The least frequent pair must be a

Double crossover

As genes get farther apart, their recombination chance increases, but it caps at...

50%

Even if two genes are at far ends of a long chromosome, they sort together at least _____% of the time

50%

Who discovered X-ray mutagenesis?

Hermann Muller

In the 1920s Hermann Muller used..

X-rays to generate fruit fly mutations

Who discovered the first Mendellian genetic disordr?

Archiblad Garrod

What is the genetic disorder that Archibald Garrod discovered called?

Alkaptonutia (dark urine) which is caused by a lack of a functionin enzyme

In 1908 Garrod published "Inborn Errors of Metabolism," describing _________, _________, __________, and _____________

Alkaptonuria, pentosuria, cystinuria, and albinism

In 1934: ___________ described, lack of an enzyme to convert _________ to tyrosine

Phenylkentonuria; phenylaline

A recombination frequency of 28% between two D. melanogaster genes suggests which of the following regarding their relative chromosomal locations?

They are linked on the same chromosome

One gene, one protein is more accurately described as

One gene, one polypeptide/RNA

The human genetic map was not completed until

1987

What did the human genetic map require?

Modern biotechnology

George Beadleand Edward Tatum were studying

Mold Neurospora

Arginine is produced

By a cluster of genes on the chromosome