Bio 203 Exam 1

What is genetics the study of

heredity and variation

what does genetics explain

why organisms have certain traits (characteristics)

Morphological traits

appearance

physiological traits

function

behavioral traits

response to environment

what are proteins

“workhorses” of living cells

What does DNA do

stores information for synthesis of all proteins & ensures that proteins must be produced by the correct cell, at the correct time, and in suitable amounts

where is genetic info stored

in the linear sequence of bases

what does a codon code for

one amino acid

Gene expression process

DNA —> proteins

two steps of gene expression

transcription + translation

Process of Transcription

DNA —> mRNA

Process of translation

mRNA —> proteins

what are phenotypes determined by

genes and environment

Gametes VS. somatic cells

gametes are haploid sex cells, while somatic cells are diploid body cells

(Human female chromosomes are diploid = 46 chromosomes)

(human gamete chromosomes are haploid = 23 chromosomes)

what are homologues 99% similar based on

size

banding pattern

centromere location

genes

what is the 1% difference between genes

alleles

what happens in G2

growth

prepares to divide

nucleus is intact

Chromosomes NOT compacted

mitosis not yet begun

what happens during M phase

mitosis + cytokinesis

DNA replication and sorting

chromosomes divide

cell division

how are haploid gametes created

meiosis

what happens during DNA synthesis

chromosomes replicate

after S phase, how many chromatids do you have

2X as many as you started with

difference between mitosis and meiosis

meiosis has two divisions and does NOT clone

when does meiosis occur

after interphase

what happens during metaphase 1

chromosomes align on metaphase plate

what happens during anaphase 1

homologues separate but sister chromatids stay together

after meiosis 1:

1 diploid —> 2 haploids

2 homologues —> 1 homolog

what happens during prophase 1

physical exchange of chromosome pieces that result in exchange of genetic information

G0 vs G1

G0 is not dividing

G1 makes the division to divide and growth occurs

what happens during prophase

nuclear envelope begins to dissociate

chromatids condense

the miotic spindle begins to form

nucleolus disappears

what happens during prometaphase

centrosomes move to opposite ends of the cell

kinetochore microtubules capture chromatids

miotic spindle formed

what happens during telophase

chromosomes reach the poles and decondense

nuclear membrane reforms

organelles segregate

when does cytokinesis occur

after mitosis (telophase)

what does cytokinesis produce

separate daughter cells

(in animals: formation of a cleavage furrow & in plants: formation of a cell plate)

what happens during metaphase

pairs of chromatids align on the metaphase plate (head to tail)

each pair of chromatids is attached to both poles by kinetochore microtubules

what happens during anaphase

the connection between sister chromatids break

kinetochore microtubules and chromatids move to each pole

major difference between meiosis 1 and 2

metaphase 1: homologues align SIDE-BY-SIDE, 2 rows of homologues

Metaphase 2: chromosomes align HEAD-TO-TAIL, 1 row of chromosomes

Anaphase 1: homologues separate

Anaphase 2: sister chromatids separate

what was hippocrates “Pangenesis” theory

“seeds” produces by all parts of body, collected, and transmitted to offspring

what was Kolreuter “Blending hypothesis” theory

factors that control hereditary traits can vary

they blend together generation by generation

what were Mendel’s two approaches in studying pea plants

self-fertilization & cross fertilization

what are genes

unit of heredity that influences traits

what are alleles

different versions of the same gene

homozygous vs heterozygous

HOMO: two identical alleles

HETER: two different alleles

what is a genotype

an individual’s specific allelic composition

what is a phenotype

the outward appearance of an individual

linked assortment vs independent assortment

linked: parental genes inherit together

independent: parental genes DONT inherit together

what are recombinants

nonparentals

law of independent assortment

alleles of one gene segregate independently of alleles of another gene

law of segregation

homologues separate (meiosis 1)

when to reject null hypothesis

P<(or equal to)0.05

multiple wild type alleles

genetic polymorphism

mutant allele

a less common version of a gene

gain of function mutations

the gene gains a new or abnormal function

may be overexpressed, producing higher levels of the protein

dominant negative mutation

the mutant protein acts to antagonize the normal protein

haploinsufficiency

the mutant is a loss-of-function allele and one wild-type copy is not enough to provide function

incomplete penetrance

allele expected to cause a certain phenotype does not

heterozygote has intermediate new phenotype

overdominance

heterozygote advantage: heterozygote is better than either homozygote

three possible explanations to overdominance

1. heterozygote has increased disease resistance

2. homodimer formation

3. Differences in protein function

universal donor vs acceptor

Type O

Type AB

sex-influenced traits

autosomal (sex influenced)

allele is dominant in one sex and recessive in the other

sex limited traits

occur in only 1 sex

responsible for sexual dimorphism

may be autosomal or sex linked

lethal alleles

mutations in essential genes

pleiotrophy

multiple effects of a single gene on the phenotype of an organism

what is pleiotrophy caused by

gene product affecting cell function in multiple ways

gene expression in different cell types

gene expression at different stages of development

IA allele

adds A antigen

IB allele

adds B antigen

gene interactions

occur when 2 or more different genes influence the outcome of a single trait

gene redundancy

another gene has the same function

female chromosome

XX (homogametic sex)

male chromosome

XY (heterogametic sex)

what does the Y chromosome do for men

Promotes male development

how does the Y chromosome lead to male development

the SRY (sex determining region Y) protein binds to DNA and distorts it, altering expression of genes leading to testis formation

female bird chromosomes

ZW (heterogametic sex) (38 autosomes) (humans have 22)

male bird chromosomes

ZZ (homogametic sex)

insect chromosomes

female: XX

male: X0 (0 signifies no chromosome)

In this system (even with XY males), it is the ratio of X
chromosomes to autosomes that determines sex
• 1 X / 2n autosomes is male
• 2 X / 2n autosomes is female

chromosomes in bees, wasps, and ants

Female is 2n
• 32 chromosomes
• From fertilized egg
Male is n
• 16 chromosomes
• From unfertilized egg

dosage compensation

Level of gene expression of many genes on sex
chromosomes is similar in both sexes, despite the
different complement of sex chromosomes
• Produce the same amount of protein

what is the lyon hypothesis

female mammals inactivate one of their X chromosomes in each somatic cell