Exam 1 Learning Outcomes

Describe the key features possessed by model organisms.

• short generation time

• production of numerous progeny

Discuss the ways that genetics is important to human health and nutrition, our environment, and agriculture.

Advances in genetics has provided insight into the nature of diseases such as cancer.

Which developments in cytology helped inform our modern-day understanding of genetics? Which hypotheses were eventually refuted?

Robert Brown - Described the cell nucleus

Mathias Jacob and Theodore Schwann - proposed the concept of the cell theory (all life is composed of cells)

*Developments in the nineteenth century led to the understanding that the cell nucleus is the site of heredity

Refuted:

Preformationism - a person inherits all of his or her traits from one parent. Blending inheritance proposed that offspring possess a mixture of the parental traits. These ideas were later shown to be incorrect

Explain central dogma and give detail on the molecules involved in each step

DNA → RNA → Protein

Describe the three types of RNA that are involved in translating a DNA sequence to a protein.

mRNA - messenger RNA : carries genetic instructions from DNA to ribosome

tRNA - transfer RNA : brings amino acids to the ribosome

rRNA - ribosomal RNA : forms the core of ribosome and catalyzes protein synthesis

For a mutation in the DNA in which one base is replaced with another, deduce how the mRNA and protein will be altered.

Silent mutation : The mRNA codon changes, but it still codes for the same amino acid.

Missense mutation : The codon changes and codes for a different amino acid.

Nonsense mutation : The codon changes into a stop codon, causing translation to end early.

Discuss the principles governing the relationship between a gene and a trait.

A gene is a segment of DNA that contains information used to produce a functional product, often a protein.

A trait is an observable characteristic, such as eye color, height, or blood type.

Discuss which molecule is most directly responsible for a trait or phenotype, which molecule codes for the phenotype and the relationship between the two.

The protein is usually the molecule most directly responsible for producing a trait because proteins perform the functions that create observable characteristics.

However, the gene (DNA) contains the instructions that determine which protein is produced.

Explain how meiosis is different from mitosis.

Mitosis - consists of a singular nuclear division accompanied by single cell division (produces genetically identical cells)

Meiosis - consist of two divisions (produces genetically variable cells)

Describe the difference between meiosis in mammalian males and females.

Males (spermatogenesis) : Begins at puberty, continuous production, meiosis produces mature sperm

Females (oogenesis) : Begins before birth, cyclic with maturation of selected oocytes , Meiosis II is completed only if fertilization occurs

Sister chromatids

two initially identical copies, held together by a centromere

Describe the stages of the cell cycle.

Interphase (G1, S, G2)

G1 - the cell grows and the proteins necessary for cell division are synthesized

S (Synthesis) - DNA is replicated, producing two sister chromatids for each chromosome

G2 - Cell continues growing, makes proteins needed for division

M phase : cell division - divides the nucleus and produces two genetically identical daughter cells

Prophase

Chromosomes condense, the mitotic spindle forms, and the nuclear envelope begins to break down.

Metaphase

Chromosomes line up at the middle of the cell.

Anaphase

Sister chromatids separate and move to opposite poles.

Telophase

New nuclear envelopes form around the two sets of chromosomes.

Cytokinesis - division of the cytoplasm producing two separate daughter cells

Genotype

set of alleles possessed by an individual organism

Genome

complete set of genetic instructions for any organism

Phenotype

The appearance or manifestation of a characteristic

Locus

A place on a chromosome where genetic information encoding a characteristic is located

Chromosomal Sex Determination

Males and females have chromosomes that are distinguishable

Genic Sex Determination

Sex is determined by genes, but the chromosomes of males and females are indistinguishable

Environmental Sex Determination

Sex is determined fully or in part by environmental effects.

Autosomes

They make up the 22 chromosomes that are non sex chromosomes.

Homologous Chromosomes

one set is inherited from the male parent and the other from the female parent

Prophase I

Chromosomes condense, the mitotic spindle forms, and the nuclear envelope begins to break down.

Metaphase I

Homologous chromosomes line up on the metaphase plate

Anaphase I

Homologous chromosomes separate and move toward the opposite poles.

Telophase I

Chromosomes arrive at the spindles and the cytoplasm divides.

Prophase II

Chromosomes recondense

Metaphase II

Individual chromosomes line up on the plate

Anaphase II

Sister chromatids separate and move towards opposite ends of the pole.

Telophase II

chromosomes arrive at the spindle and the cytoplasm

Law of Segregation

two alleles separate into different gametes

Independent Assortment

unlinked genes assort independently

Test cross

cross with a homozygous recessive individual

Crossing over (source of genetic variation)

Homologous chromosomes exchange DNA during Prophase I

Independent Assortment (source of genetic variation)

Homologous pairs orient randomly during metaphase I

Random fertilization (source of genetic variation)

any compatible sperm may fertilize an egg

Diploid 2n

two sets of chromosomes

Haploid n

One set of chromosomes

“AND”

multiply independent probabilities

“OR”

add independent probabilities