AP BIO UNIT 5: Heredity

Heredity

Heredity

the transmission of traits from one generation to the next by inheriting DNA from a single parent (asexual reproduction) or from two parents (sexual reproduction)

Chromosomes

the packed and organized structures of DNA found in cells

Eukaryotic chromsome

consists of a single molecule of DNA wrapped around proteins called histones

Histones

function to package and organize the DNA

Linked

genes that are located on the same chromosome

Linear shape

the shape of eukaryotic DNA

Bivalent chromosomes

chromosomes that consist of 2 copies of the original chromomsome

Centromere

the structure that holds chromatids together at the center

Chromatids

two copies of a chromosome

Autosomes

chromosomes that are not involved in gender determination

Sex chromosomes

chromosomes that are involved in the process of gender determination

Prokaryotic chromosome

circular DNA shape

Nucleoid

the region in the cell where prokaryotic DNA is found

Plasmid

a small, circular, double-stranded DNA molecule that is distinct from a cell’s chromosomal DNA

Conjugation

the process where plasmids can be exchanged between bacterial cells

Gene

a segment of DNA which codes for a single polypeptide or protein

Genome

an organism’s complete set of DNA

Haploid

refers to cells that have only one copy of each type of chromosome

Dipolid

cells that have two copies of each type if chromosome

Locus

the location of a gene on a chromosome

Asexual reproduction

reproduction that involver one parent and produces genetically identical daughters

Sexual reproduction

reproduction that involves 2 parents and produces genetically different offspring

Meiosis

a specialized type of nuclear division that reduces the chromosomes number by half, creating four haploid cells genetically distinct from the parent cell

Prophase I

the homologous chromosomes condense and become visible as the x shape pair up and exchange genetic information by crossing over

Homologous chromosomes

Chromosomes of the same type/number

Synapsis

the pairing of 2 chromosomes

Crossing over

the physical exchanging of segments of DNA

Metaphase I

the two members of each homologous pair of bivalent chromosomes align on each side of the metaphase plate

Anaphase I

one member of each homologous pair of chromosomes is pulled toward each pole of the cell by the microtubules of the spindle apparatus

Telophase I

the homologous chromosome pairs reach the poles of the cell, the spindle fibers disappear, nuclear envelopes form around each set of chromosomes

Interkinesis

a short interphase-like period that occurs between meiosis I and meiosis II

Prophase II

Similar to prophase II and no synapis or crossing over occurs during this stage

Metaphase II

the chromosomes in both cells become arranged on the metaphase plate

Anaphase II

the centromeres of each chromosome (in both cells) separate and the sister chromatids move towards opposite poles of the cell

Telophase II

a nuclear envelope forms around each set of chromosome and cytokinesis occurs producing 4 haploid daughters

Spermatogensis

the process of sperm creation

Oogenesis

the process of egg creation

Nondisjunction

the failure of homologous chromosomes or sister chromatids to separate properly during cell division

Aneuploidy

results in daughter cells with abnormal chromosome numbers

Karyotype

a picture of a person’s chromosomes

Chromosomal mutations

large chunks of chromosomes (but not entire chromosomes) are affected

Duplication

a chromosome ends up with two or more copies of a gene segment

Deletion

a chromosome ends up with no copies if a particular gene segment

Inversion

a chromosomal region is flipped around so that it points in the opposite, wrong direction

Translocation

a piece of one chromosome is attached to another non-homologous chromosome

Gregor Mendel

the “Father of Genetics”; groundbreaking work with inheritance in pea plants

Law of Dominance

when parents with pure, contrasting traits are crossed together, only one form of the trait appears in the next generation

Law of Segregation

states that alleles segregate randomly into gametes

Law of Independent Assortment

alleles of 2 or more different genes get sorted into gametes independently of one another

Trait

a genetically determined characteristic

Alleles

refers to different versions of a gene

Doninant

more likely to be expressed

Recessive

less likely to be expressed

Homozygous

an organism is said to be homozygous or pure bred for a trait if the two alleles it possesses for the trait identical (TT or tt)

Heterozygous

an organism is said to be heterozygous or a hybrid for a trait if the two alleles is possesses for the trait are different (Tt)

Phenotype

refers to the physical traits or appearance of an organism

Genotype

refers to an organism’s genetic (DNA) make-up for a trait

Punnet Square

a chart which shows the possible genotypic outcomes for a mating cross based on the parent’s genotype

Monohybrid Cross

a cross in which only one trait is analyzed

Dihybrid Cross

a cross in which the inheritance of two traits is analyzed at the same time

Linked genes

occur on the same chromosome, and therefore, tend to be inherited together

Incomplete dominance

a form on intermediate inheritance in which one allele for a specific trait is not completely expressed its paired allele

Codominance

a condition in which both alleles in a pair are expressed at the same time

Multiple alleles

when 3 or more alternative forms of a gene (allele) can occupy the same locus

Pleiotropy

a condition in which one gene affects multiple (seemingly unrelated) characteristics

Epistasis

a condition in which a gene at one locus affects a gene at a second locus

Polygenic Inheritance

occurs when a trait is governed by two or more sets of alleles

Multifactorial traits

those controller by multiple genes that are also affected by physiological and environmental influences

Lethal alleles

certain allele combinations which are lethal and prevent the birth of individuals with certain genotypes

Pedigree chart

a diagram showing the lineage or genealogy of an individual and all the direct ancestors, usually to analyze or follow the inheritance of trait

Mode of Inheritance

the manner in which a genetic trait or disorder is passed from one generation to the next

Autosome

a non-sex chromosome

X & Y chromosomes

sex chromosomes

Carrier

an individual who possesses only one copy of a recessive allele

Gene linkage

genes are linked if they are found on the same chromosome

Phenotypic plasticity

occurs when individuals with the same genotype exhibit different phenotypes in different environments