Phenotypes, Genotypes, Reproduction, & Inheritance

Genotype

information stored in DNA

Phenotype

all structures, processes, and behaviors of an organism

Genotype + Environment →

Phenotype

Phenotypic changes are due to environment are

not heritable

Phenotypic Plasticity

the ability of individuals with a particular genotype to express different phenotypes as a result of environmental differences

Monogenic traits

controlled by a single gene

Polygenic traits

due to the action of multiple genes interacting with one another through integrated pathways

Phenotypic Variation)

individuals vary for a given trait in a population; the result of the interaction between information from the environment and genotype

Continuous Variation

average phenotype that most individuals cluster around; aka height

Discrete variation

a trait typically exhibits either one phenotype or another

V_G

variation in the population’s genotype

V_E

variation in the population’s environment

V_GE

specific interactions of genotype and environment

2 non-random mechanisms of evolution

natural selection and sexual selection

What are the three key requirements for phenotype selection?

phenotypic variation, heritability, overproduction of offspring

Heritability

genotype component of phenotype to be passed on to offspring

Natural Selection vs. Sexual Selection

NS- differential survival; SS- differential reproductive success

DNA

double helix of base pairs containing the fundamental hereditary information of a living organism

Chromatin

DNA combined with proteins; heterochromatin & euchromatin

Heterochromatin

condensed, densly packed

Euochromatin

uncondensed, diffuse

Chromosomes

discrete structures composed of chromatin; can be totally condensed or certain parts extended

Ploidy

number of types of chromosomes in a cell

Haploid

1N; one set of chromosomes; one version of each gene

Diploid

2N; two complete (and different) sets of chromosomes; 2 versions of each gene

Polyploid

more than two versions of info; ex: tetraploid, 4N

What are the mechanisms to preserve DNA sequence?

proofreading, mismatch repair, replace damage bases

Mitosis

eukaryote cell division that results in 2 genetically identical daughter cells

What does mitosis end with?

two identical 2N cells

Meiosis

eukaryote cell division that results in 4 genetically unique daughter cells

What does Meiosis 1 end with?

two genetically unique 1N cells

What does Meiosis (II) end with?

4 genetically unique 1N cells

Crossing Over

the mechanism where homologous chromatids exchange corresponding segments of DNA; change info only with exchanging with chromatid from other parent

Independent Assortment

the mechanism where homologous pairs line-up randomly in Meiosis I, leading to random chromosome combinations in daughter cells

How do you increase variation?

DNA repliation, meiosis (crossing-over + independent assortment), synagmy

What is the purpose of sex?

genetic recombination so offspring genotypes are unique from parental genotypes

Advantages of Sexual Reproduction

Hedging bets; Red Queen hypothesis

Disadvantages of Sexual Reproduction

offspring only receive half of each parent’s genes; can be hard to find mate; potential mates must be genetically compatible; offspring may be less fit than either parents

Hedging Bets

if environmental (abiotic/biotic) conditions change, having wide range of phenotypes in offspring will ensure some will survive/pass on genes

Hedging Bets Example

Peppered Moth vs. Industry

Red Queen Hypothesis

other organisms are constantly evolving biotic conditiosn that genetic recombination creates favorable combinations of genes to rapidly keep up

Gene

a segment of DNA that contains the instructions for building a specific protein or performing a particular function

Locus

the physical location (singular) of a gene sequence on the DNA strand

Loci

the physical location (multiple) of a gene sequence on the DNA strand

Allele

functionally different variants of a gene; diploid organisms have 2 alleles of each gene

Homozygous Alleles

diploid individual contains two functionally identical alleles of a particular gene

Heterozygous Alleles

a diploid individual posessing two different alleles for a gene

Simple Dominance

some alleles are dominant over others (will be expressed if there is 1 allele) and some are recessive (need 2 alleles to express)

Partial or Incomplete Dominance

each genotype is associated with a distinct phenotype; can be varying in the range between dominant and recessive genotypes

Semi-Dominance

the heterozygote’s phenotype is exactly intermediate between the phenotype of each homozygote

Co-Dominance

both alleles contribute equally to the phenotype; often dominate over other alleles

In Dachshunds, hair length is controlled by alleles at the FGF5 locus. A cross between a short hair and long hair parent produces all short haired puppies. What is the mode of inheritance?

simple dominance

In some sea anemones, a neon AnthoYFP allele encodes for a visibly brighter variant. Here are some phenotypes of homozygote and heterozygote anemones. What is the mode of inheritance?

partial or incomplete dominance

What is the mode of inheritance for blood?

co-dominance

What is the mode of inheritance of the fruit?

semi-dominance

Many genes have multiple alleles, which increases the possible number of phenotypes for the trait. There are 4 alleles for rabbit coat color shown here:

• The C allele leads to dark

grey fur

• The cchd allele leads to a

lighter grey fur

• The ch allele leads to

restricted pigment

deposition

• The c allele leads to no

pigment deposition

What is the mode of inheritance?

simple dominance

Epistasis

one gene alters/masks/interacts with the phenotypic effect of another gene

Pedigree inheritance

the study of how traits are transmitted across generations by analyzing family trees to identify genetic patterns

Autosomal Dominant Inheritance

only one copy of the altered allele is needed to show trait/disorder; no carriers

Autosomal Recessive Inheritance

must inherit two copies of altered gene to show trait/disorder; can have carriers (have gene but no symptoms- heterozygotes)

Genetic Linkage

genes on the same chromosomes; will not segregate independently

Completely linked genes

genes close together bc cross-over between them is unlikely

Incompletely linked genes

genes are far apart so cross-over is more likely

Aneuploidy

atypical number of chromosomes (too many or two few)

Gene Dosage

number of genes; can be changed with too many or too few chromosomes (aneuploidy)

Reproduction

process that allows organisms to create new individuals

Sexual Reproduction produce

genetically distinct offspring

Asexual Reproduction produce

genetically identical offspring

No alterations

diploid organism has germ cells that undergo meiosis to produce gametes for sexual reproduction

Alterations of Generations

Cells of diploid organism undergo

meiosis to produce spores, which

both grow AND produce gametes

via mitosis

Alternation of Strategies

Diploid organism can undergo

asexual reproduction,

OR produce gametes via meiosis

for sexual reproduction

What are the ways multicellular organisms reproduce?

no alternation, alteration of strategies, alternation of generations

Mechanisms of Asexual Reproduction for unicellular organisms

binary fission (Bacteria/Archaea) & binary fission through mitosis (eukaryotes)

Mechanisms of Asexual Reproduction for Multicellular Organisms

parthenogenesis, budding, regeneration, vegetative propagation

Parthenogenesis

development of offspring from unfertilized gametes

Budding

new individuals form as outgrowth from body of older individual

Regeneration

growth of new individual from pieces of older individual

Vegetative Propagation

term for budding/regeneration in plants

Mechanisms of Sexual Reproduction

spawning, direct transfer, indirect transfer

Spawning

external or internal fertilization; release gametes into the environment

Direct Transfer

transfer of gametes via intermittent organ (internal fertilization)

Indirect Transfer

transfer of gametes via spermatophore; internal fertilization

Gametes

haploid (1N) cells that fuse together in sexual reproduction

Organisms that typically produce fewer, larger gametes are considered

female

organisms that typically produce more, smaller gametes are considered

males

Can some organisms produce both types of gametes?

yes

Sexes can be defined by

the type of gamete produced (phenotype)

Environment Factors for Sex Determination

Hormone levels, Temperature, Size, Social Cues, Access to

resources (ex. food), Location

Phenotype Factors for Sex Determination

Gamete produced, Primary Sexual

characters, Secondary Sexual

characters

Genotype Factors for Sex Determination

Ploidy (N vs 2N) & Sex

chromosomes (if present) aka XX & XY + ZZ & ZW

What can affect Sex Determination?

Individuals may make 1, both, or neither type of gamete, + Cells, tissues, organs that aid in gamete production, + Structures for gamete release or delivery, + Mechanisms/structures tied to development

Temperature Determining Sex

in many reptiles and some fish; proportion of sex depends on nest temperature and parental care can affect it too

Access to Food Determining Sex

in some eusocial insects (bee, ants, wasps); being fed a special food throughout development can determine sex

Naked Mole Rat Determining Sex

reproductives ones suppress the reproductive development of other females by expressing certain pheromones in their urine

Reproductive Parasite in Determining Sex

Wolbachia infect anthropods and nematods which may preferentially kill-off male larvae, feminization of chromosomal males, parthenogenesis, mating incompatibility

Location in Determining Sex

Bonellia viridis larvae on sea floor develop female morphology but land on female proboscis enter gut and develop male morphology

Age/Size or Social Cues

some fish begin life as one sex, then change to another upon reaching a given size/age or social cue with hierarchy

Monoecious

single individual that produces both male and female gametophytes; may be capable of self-pollination and/or cross-pollination

Dioecious

female and male gametophytes are produced by different individuals who are incapable of self-pollination

Gymnosperms

2 types of cones; seed cones- egg-producing gametophyte; pollen cones- pollen = sperm-producing gametophyte