AP Biology Unit 5: Heredity Study Guide

Gametes

a haploid reproductive cell, such as an egg or sperm , that is formed by meiosis or is the descendant of cells formed by meiosis; they unite during sexual reproduction to produce a diploid zygote

somatic cells

any cell in a multicellular organism except a sperm or egg or their precursors

locus

a specific place along the length of a chromosome where a specific gene is located

asexual reproduction

the generation of offspring from a single parent that occurs without the fusion of gametes. In most cases the offspring are genetically identical to the parent

clone

a group of genetically identical individuals or cells (some changes known as mutations happen)

sexual reproduction

reproduction arising from fusion of 2 gametes

life cycle

the generation to generation sequence of stages in the reproductive history of an organism

karyotype

a display of the chromosome pairs of a cell arranged by size and shape

homologous chromosomes

a pair of chromosomes of the same length, centromere position and staining pattern that possesses genes for the same characters at corresponding loci. one is inherited from father and the other from the mother

sex chromosomes

a chore,osomes responsible for determining the sex of an individual

autosomes

a chromosome that is not directly involved in determining sex; not sex chromosomes

diploid cells

a cell containing 2 sets of chromosomes (2n) 1 set inherited from each parent (humans: 2n=46)

haploid cells

a cell containing only one set of chromosomes (n) (humans: n=23; 22 autosomes and 1 sex chromosome)

fertilization

the union of haploid gametes to produce a diploid zygote

zygote

the diploid cell produced by the union of haploid gametes during fertilization; a fertilized egg

meiosis

a modified type of cell division in sexually reproducing organisms consisting of 2 rounds of cell division but only 1 round of DNA replication. results in cells with ½ the number of chromosome sets as the original cell

alternation of generations

a life cycle in which there is both a multicellular diploid form and a multicellular haploid;

sporophyte

a multicellular diploid form

gametophyte

a multicellular haploid form

meiosis I

the first division of a 2 stage process of cell division in sexually reproducing organisms that results in cells with ½ the number of chromosome sets as the original cell

meiosis II

the second division of a 2 stage process of cell division in sexually reproducing organisms that results in cells with ½ the number of chromosome sets as the original cell

Prophase I

each chromosome pairs with its homolog, aligned gene by gene and crossing over occurs. each homolog has a chiasmata. centrosome movement, spindles form, nuclear envelope breaks down, and chromosomes condense. microtubules attach to kinetochores and move pairs to the metaphase plate

crossing over

the DNA molecules of non sister chromatids are broken(by proteins) and move pairs to metaphase plate

chiasma

each homolog has one of more of these X shaped regions where crossovers have occurred

metaphase I:

homologs are arranged at the plate with one chromosomes of each pair facing the pole. each pair is lined up independently of other parts (Ind assortment)

anaphase I

breakdown of proteins that are responsible for sister chromatid cohesion. the homologs move towards opposite poles

telophase I and cytokinesis

when telophase I begins each half of the cell has a complete haploid set of duplicated chromosomes. cytokinesis occurs simultaneously. in some species, chromosomes decondense and form nuclear envelopes. no chromosome duplication occurs between Meiosis I and II

prophase II

a spindle apparatus forms. in late Prophase II, chromosomes, each still composed of 2 sister chromatids, are moved by microtubules to metaphase plate

metaphase II

chromosomes positioned at plate. Because of crossing over in Meiosis I the 2 sister chromatids are not identical

anaphase II

breakdown of proteins holding the sister chromatids together allowing the chromatids to separate and move to opposite poles. each chromatid has now become an individual chromosome

telophase II and cytokinesis

nuclei form, chromosomes decondense, and cytokinesis occurs. the metabolic division of one parent cell produces 4 daughter cells each with a haploid set of unduplicated chromosomes

synaptonemal complex

a zipper like structure composed of proteins which connects a chromosome to its homolog tightly along their lengths during part of prophase I of meiosis

independant assortment

the 1st metic division results in each pair sorting its maternal and paternal homologs into daughter cells independently of every other pair because each pair of homologs is positioned independently of the other pairs at metaphase I

recombinant chromosomes

a chromosome created when crossing over combines DNA from parents into a single chromosome

character

an observable heritable feature that may vary among individuals

trait

one of 2 or more detectable variants in a. genetic character

true breeding

referring to organisms that produce offspring of the same variety over many generations of self-pollination

hybridization

in genetics, the mating or crossing, or 2 true breeding varieties

p generation

the true breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance

F1 eneration

the 1st filial, hybrid (heterozygous) offspring arising from a parental cross

F2 generation

the offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation

alleles

any of the alternative versions of a gene that may produce distinguishable phenotype effects

dominant allele

allele that is fully expressed in the phenotype of a heterozygote

recessive allele

an allele whose phenotypic effect isn’t observed in a heterozygote

law of segregation

menders first law, stating that the 2 alleles in a pair seperate from each other (segregate) into different gametes during gamete formation

punnet square

a diagram used in the study of inheritance to show the predicted genotypic results of random fertilization in genetic crosses between individuals of known genotype

homozygote

having 2 identical alleles for a specific gene

heterozygote

having 2 different alleles for a given gene

phenotype

the observable physical sn physiological traits of an organism =, which are determined by its genetic makup

genotype

the genetic makeup, or set of alleles, of an organism

testcross

breeding an organism of unknown genotype with a homoaygous recessive individual to determine the unknown genotype. the ratio of phenotypes in the offspring reveals the unknown genotype

monohybrid

an organism that is heterozygous with respect to a single gene of interest. all the offspring from a cross between parents homologous for different alleles are this

monohybrid cross

a cross between 2 organisms that are heterozygous for the character being followed

dihybrids

an organism that has heterozygous with respect to 2 genes of interest . all the offspring form a cross between parents doubly homozygous for different alleles are this

dihybrid cross

a cross between 2 organisms that are each heterozygous for both the characters being followed

law of independent assortment

menders 2nd law. stating that each pair of alleles segregates, or assorts, independently of each other pair during tgamete formation’ applies when genes for 2 characters are located on difference pairs off homologs or when they are far enough apart on the same chromosomes to behave as though they are on different chromo0somes

multiplication rule

a rule of probability stating that the probability of 2 or more independent events occurring together can be determined by multiplying their individual probabilities

addition rule

a rule of probability stating that the probability of 2 or more Mutually exclusive events occurring can be determined by adding their individual probabilities

complete dominance

the situation in which the phenotypes of the heterozygote and dominant are distinguishable

incompltete dominance

the situation in which the phenotype of heterozygotes is immediate between the phenotypes of individuals homozygous of either alleles

codominance

the situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the pheotype in separate sistinguishable

pleiotrophy

the ability of a single gene to have multiple effects.

epistasis

a type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene

quantitative characters

a heritable feature that varies continuously over a range rather than in either-or fashion

polygenic inheritance

an additive effect of 2 or more genes on a single phenotypic character

multifactorial

referring to a phenotypic character that is influenced by multiple genes and environmental factors

pedigree

a diagram of a family tree with conventional symbols showing the occurrence of heritable characters in parents and offsprings over multiple generations

carriers

an individual who is heterozygous at a given genetic locus for a recessively inherited disorder

wild type

the phenotype most commonly observed in natural populations; also refers to the individual with that phenotype (+ identifies wile type trait)

sex linked gene

a gene located on either sex chromosome. most sex linked genes are on the X chromosome and show distinctive patterns of inheritance; there are few genes on the Y chromosome

X-linked gene

a gene located on the X chromosome; such genes show a distinctive pattern of inheritance

barr body

a dense object lying along the side of the nuclear envelope in cells of female mammals, representing a highly condensed, inactive X chromosome

linked genes

genes located close enough together on a chromosome that they tend to be inherited together

genetic recombination

general term for the production of offspring with combos of traits that differ from those found in either parent

parental types

an offspring with a phenotype that matches one of the true breeding parental phenotypes; also refers to the phenotype itself

recombinant types

an offspring whose phenotype differs from that of the true-breeding parent generation parents; also refers to the phenotype itself (AKA recombinants)

crossing over

the reciprocal exchange of genetic material between non sister chromatids during prophase I of meiosis

genetic map

an ordered list of genetic loci (genes of other genetic matter) along a chromosome

linkage map

a genetic map based on the frequencies of recombination between markers during crossing over of homologs

map units

a unit of measurement of the distance between genes. one map unit is equivalent to a 1% recombination frequency

nondisjunction

an error in meiosis or mitosis in which members of a pair of homologs or sister chromatids fail to separate properly from each other

aneuploidy

a chromosomal abberation in which one or more chromosomes are present in extra copies or are deficient in numbers

monosomic

referring to a diploid cell that has only one copy of a particular chromosome instead of the normal 2

trisomic

referring to a diploid cell that has 3 copies of a particular chromosome instead of the norma 2

polyploidy

a chromosomal alteration in which the organism processes more than 2 complete chromosome sets. it is a result of an accident of cell division

duplication

an abberation in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is duplicated

inversion

an abberation in chromosomes structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated

translocation

an abberation in chromosome structure resulting from attachment of a chromosomal fragment to a non homologous chromosome

look over statement

for chi squared