Biology Chapter 9 SQ1

cross fertilization

a hybridization of offspring of two varieties

self fertilization

the fusion of sex cells produced by the same individual (offspring of one variety)

flower

reproductive organ, can be male or female, can make sperm or egg cells

character

a heritable feature that varies among individuals

trait

varient or alternate form for a character

allele

an alternate version of a gene usually represented by capital or lowercase letter

homozygous

having two identical alleles for the given genes

heterozygous

having two different alleles for the given genes

gene

a segment of DNA that codes for a polypeptide

phenotype

genetics distinguished between its physical form

genotype

genetic makeup

punnet square

a diagram used in the study of inheritance to show the results of random fertilization

true breed

sexual reproduction produce offspring with inherited traits identical to those of the parents

cross

a mating of two sexually reproducing individuals

P generation

true-breeding parents

F1 generation

true-breeding offspring

F2 generation

F1 plants self-fertilize offspring

Mendel’s experiments

1) Mendel produced individuals that are pure for a particular trait (true breed or strain) by self-pollinating a plant repeatedly to obtain that one trait a number of times and only that trait is observed through multiple generations and self-pollinations.

2) Mendel then crossed two pure plants for a particular trait, a purple flower and a white flower. 'The pure/strain/true breed parents are called the P generation (parental) and their offspring/hybrids are called the F1 generation (filial).

3) The next generation is obtained by self-fertilizing/pollinating the F1 generation to get the F2 generation.

Mendel’s observations

1) There are alternative versions of genes that account for variations in inherited characteristics.

2) For each character, an organism inherits two alleles, one from each parent.

3) If the two alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele. The other has no effect on the appearance and is called the recessive allele.

4) A sperm or egg only carries only one allele for each inherited character because allele pairs separate from each other during the production of gametes.

The Law of Segregation

when sperm and egg unite at fertilization, each contributes its allele, restoring the paired condition in the offspring. a pair of alleles segregate during gamete formation

dominant allele

a pair of alleles that determines the organism’s appearance

recessive allele

a pair of alleles with no effect on the organism’s appearance

Principle of Independent Assortment

He concluded that seed color was independent of seed shape during gamete formation. He further reasoned that each pair of alleles (seed shape and seed color) segregates independently, Principal of Independent Assortment. In other words, the different characters (pea color and pea shape) are inherited independently from each other.

gene locus

the location of a gene on a chromosome

dihybrid cross

a mating of parental varieties differing in two characters

incomplete dominance

a single gene locus trait of inheritance in which the phenotype of a heterozygote is intermediate between the phenotypes of the two types of homozygotes

multiple allele traits

a single gene locus trait in which genes are found in populations in more than two versions

ex. ABO blood group in humans involve 3 alleles of a single gene → A, B, AB, and O

codominance

a single gene locus heritable trait in which both alleles are expressed in heterozygous individuals who have type AB blood

plietrophy

one gene that influences multiple characteristics

ex. sickle cell disease is one amino acid that is different than a normal chain and causes many issues

polygenic inheritance

the additive effects of two or more genes on a single phenotypic character (more than one gene location)

ex. hair, skin color, nose shape

linked genes

genes located close together on the same chromosome tend to be inherited together

ex. sweet pea genes for flower color and pollen shape are located on the same chromosome

sex-linked gene

a gene located on either sex chromosome

ex. male phenotype relies entirely on his single x-linked gene

crossing over

the exchange of genetic material between homologous chromosomes

recombination frequency

equivalent to the crossing over frequencies for genes on the same chromosome. The recombination/crossing over frequencies or % of unexpected outcomes/ combinations is equivalent to a map unit. Map unit is equal to the % of crossing over

ex. fruit flies have a 17% frequency of a recombination

monohybrid cross

an experimental mating of individuals that are heterozygous for the character being followed

test cross

a mating between an individual of unknown genotype and a homozygous recessive individual

rule of multiplication

a probability of an event is the product of the separate probabilities of the independent events

rule of addition

the probability of an event can occur in two or more alternative ways is the sum of the separate probabilities of the different ways

chromosome theory of inheritance

a theory that states genes have specific loci on chromosomes that involve different chromosome behavior like linkage, segregation, and independent assortment

the X-Y system

a sex determination system in which the sex of an individual is determined by the male chromosomes

ex. humans

the X-O system

a sex determination system in which the Y chromosome is absent yet the sex of an individual is determined by the male

ex. grasshoppers

the Z-W system

a sex determination system in which the sex is determined by the female chromosomes

ex. birds and plants

the chromosome number system

a sex determination system in which the sex of an organism is determined by their chromosomal number

ex. bees and ants

hermaphroditic

individuals that produce both sperm and egg

monoecious

plants that produce sperm and egg

pedigree

a family genetic tree representing the occurence of heritable traits in parents and offspring accross a number of generations