AP Bio Unit 5 Study Guide

Starred terms are in the notes/textbook, but they have not appeared in class. High likelihood they are irrelevant for the test.

Sister Chromatid

part of a replicated chromosome

Homologous Chromosomes

two chromosomes that contain the same genes

Karotype*

snapshot of an individual’s chromosome (taken during metaphase)

Sex Chromosomes

chromosomes that determine the sex of the offspring

Autosomes

non-sex chromosomes (44 in humans or 22 pairs)

Gametes

reproductive cells like sperm and egg

Somatic Cells

body cells which are not gametes

Haploid Cells

cells which have one copy of each chromosome

Diploid Cells

cells with complete genetic information

Meiosis

the process in which gamete cells reproduce from one to four gametes

Synapsis

connection of homologous chromosomes to each other in meiosis

Crossover

swap of homologous regions between chromosomes and exchange of genes

Chiasma*

physical link between non-sister chromatids where crossover can occur

Tetrad

structure which describes homologous chromosomes linked up as one

Independent Assortment

replicated pairs can line up in different and cause genetic variation in daughter cell

Blended Hypothesis

a hypothesis which argues parent traits mix together in daughter cells

Particulate Hypothesis

heritable units are passed on and remain separate like cards

Law of Segregation

law which states that heritable traits separate in the formation of gametes

Genes

heritable factors which influence traits

Alleles

variants of a gene

Phenotype

observable trait of an organism that is determined by genotype

Genotype

genetic makeup of an organism

Homozygous Dominant

organism which has two copies of the dominant allele

Homozygous Recessive

organism which has two copies of the recessive allele

Heterozygous

organism which has one dominant and recessive allele for a gene

Test Cross

crossing a parent with a recessive phenotype to test the dominant genotype of the parent by observing the F2 generation

Monohybrid Cross

cross between organisms with variation in one gene

Dihybrid Cross

cross between organisms with variation in two genes

Heredity

transmission of traits from one generation to the next

Variation

difference between parent and offspring in genetic makeup

Genetics

scientific study of heredity and inherited variation

Genes

coded information which are inheritable

Locus

gene’s specific location along the length of the chromosome

Asexual Reproduction

single individual is the sole parent and passes their genes

Clone

a group of genetically identical individuals

Sexual Reproduction

reproduction where two parents give rise to offspring with an unique combination of genes

Life Cycle*

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

Fertilization

union of gametes where their nuclei fuse

Zygote

resulting fertilized egg from fertilization

Alternation of Generations*

a type of life cycle where a species reproduces sexually and asexually every other generation

Synaptonemal Complex*

a zipper-like structure where genetic info between homologous chromosomes is exchanged

Recombinant Chromosomes

individual chromosomes which carry genes from two parents

Chi-Square

a method used to quantify variation between expected and observed values

Null Hypothesis

difference between observed and expected is insignificant

Degrees of Freedom

number of categories - 1

Multiplication Rule

multiplication of two independent probabilities to get the probability of both occuring

Addition Rule

the probability of any two or more mutually exclusive event by adding the individual probabilities

Complete Dominance

an instance where the heterozygote is phenotypically indistinguishable from the dominant homozygote

Incomplete Dominance

when neither allele is completely dominant and the heterozygote looks phenotypically similar to both alleles

Codominance

an instance in which two alleles both affect the phenotype and neither override the other

Pleitropy

an instance where one gene affects more than one phenotype

Epistasis

phenotypic expression of a gene at one locus is affected by another gene in another locus

Quantitative Characters

characters which vary along a continuum like skin color

Polygenic Inheritance

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

Multifactorial

phenotypes which are influenced not just by genotype but also the environment

Pedigree

a collection of a family’s history to describe traits across generations

Carriers

heterozygotes which can pass on alleles for disorders

Lethal Allele

allele which when inherited causes death

Chromosome Theory of Inheritance

theory that the genes are not independently assorted but rather chromosomes

Sex-Linked Gene

a gene located on a sex chromosome

X-Linked Gene

genes on the X chromosome

Linked Genes

genes located near each other on a chromosome which are often inherited together

Genetic Recombination

production of offspring with combinations that differ from either P generation parent

Parental Types

offspring that are identical to the parents

Recombinant Types

offspring that are a mix of the phenotypes of the parents

Genetic Map

an ordered list of the genetic loci along a particular chromosome

Cytogenetic Maps

maps which locate genes with respect to chromosomal features

Nondisjunction

when homologous chromosomes or sister chromatids do not properly disassemble and move apart

Aneuploidy

a zygote which has an abnormal # of a particular chromosome

Monosomic

zygote which is missing one chromosome (2n - 1)

Trisomic

zygote which has one extra chromosome

Polyploidy

organisms which have more than two sets of chromosomes

Deletion

the loss of a chromosomal fragment

Duplication

an instance where a lost chromosomal fragment attaches to its sister chromatid

Inversion

an instance where a chromosomal fragment reattaches but is attached in reverse order

Translocation

attachment of a chromosomal fragment to a new non-homologous chromosome

SRY Gene

sex-determining region located on the Y chromosome

Recombinant Frequency

the frequency of recombinants in offspring, calculated by # of recombinants / # of total offspring

Gene Mapping

a chromosome map that shows the relative location of a gene on a chromosome