Genetics Exam #1

Character (characteristic)

Some observable feature

Ex. Pea color, stem length

Phenotype (trait)

The particular manifestation of a character, determined by an allele

Ex. Yellow or green, tall or short

Gene

A region of DNA that determines character

Ex. Ygene or Rgene

Allele

One of two (or more) alternate forms of a gene

Ex. Y or y, R or r

Mono hybrid P generation

True breeding, homozygous, makes just one type of gamete

Mono hybrid cross key

Assess the genotype (unknown) of an individual by looking at the phenotype of the offspring

Definition of dominance

The phenotype in the hybrid defines dominance

Genes vs. phenotype

Genes you cannot see, phenotypes are visible

Segregation

Alleles that combine in the hybrid separate when gametes are produced

Variation reveals…

Hidden order

Mono hybrid cross results

3 A- (dominant) : 1 aa (recessive)

Dihybrid cross ratio

9:3:3:1

Mendel’s 2 patterns

Segregation & independent assortment

Independent assortment

In a cross with multiple genes on separate chromosomes, they will segregate independently

Segregation

A single allele is selected at random from a diploid parent when gametes are produced

Addition Rule

Getting one or the other of two mutually exclusive events

Multiplication rule

Getting one event and another second event

Dihybrid test cross

RrYy x rryy

Square

Male

Circle

Female

Shaded

Affected with trait

Prokaryotic cell

No nucleus, small, one circular DNA molecule, minimal or no histones, small amount of DNA, no organelles

Eukaryotic cell

Contains nucleus, larger size, multiple linear DNA molecules, complex with many histones, large amount of DNA, contains organelles

Viruses

Not alive, neither eukaryotic or prokaryotic

Cell division in prokaryotes

Binary fission

Cell division in eukaryotes

Mitosis and meiosis

Jobs of cell division

Divide cellular components and divide the genome

Similarities between binary fission and mitosis

Exact duplicate

Binary fission keys

Exceptionally fast, single circular chromosome and small simple cells (origin of replication)

Sister chromatids

Exact copies (from S phase) held together

Homologous chromosomes

Pairs from mom and dad, have same set of genes but often different alleles

Centromere

Region where the chromosome is most restricted, where the spindle fibers attach

Molecular def of centrosome

Special histones mark this region, often special DNA sequences

Functional def of centromere

Where the kinetochore (signaling hub/ huge protein machine) assembles and binds to microtubules

Challenges of eukaryotic cell division

Accurate cell division (mitosis) and accurate production of gametes (meiosis)

Interphase

G1- growth

Checkpoint

S phase- DNA synthesis

G2- gap 2

Checkpoint

Mitosis or meiosis

Interphase keys

Centrosomes duplicated, DNA duplicated but not condensed

Prophase keys

Chromosomes condense, each has two chromatids, mitotic spindle forms

Prometaphase keys

Nuclear mem disintegrates, spindle microtubules attach to kinetochores of chromatids

Spindle assembly checkpoint

Metaphase- anaphase transition, wait until all kinetochores are biattached (both sides), any unattached kinetochore halts progress with (wait for me) signal

Metaphase keys

Chromosomes line up on metaphase plate

Anaphase keys

Cleavage (cutting) of cohesin releases sister chromatids and they move toward opposite poles

Telophase keys

Chromosomes arrive at spindle poles, nuclear mem reforms

_ produces exact genetic duplicates

Mitosis

_ produces genetic variation

Meiosis (sexual reproduction)

Crossing over

Shuffles the combination of alleles within a single chromosome

2 ways to shuffle alleles

Crossing over and random alignment of bivalents

Segregation

Caused by random orientation of bivalents