AP BIO Unit 5 + 6

gene

physical and functional unit of heredity, a sequence of DNA that codes for a protein.

asexual reproduction

form of reproduction that produces offspring that are genetically identical to the parent

sexual reproduction

mixing of genetic material from two individuals to produce genetically unique offspring

somatic cell

all the cells of a multicellular organism except the gametes or reproductive cells

diploid

cell, nucleus, or organism containing two sets of chromosomes (2n)

homologs

chromosome pairs - one inherited from each parent - that are the same length and centromere position *

autosomes

any of the non-sex chromosomes

sex chromosomes

the pair of chromosomes (often the 23rd pair in humans) that directly determine the biological sex of an organism *

haploid gametes

specialized reproductive cells (sperm and egg) that contain only a single set of chromosomes *

meiosis

a nuclear division process that results in four haploid cells

fertilization

union of two haploid cells from two individual organisms

zygote

the initial, single diploid (\(2n\)) cell formed when a haploid (\(1n\)) sperm and a haploid (\(1n\)) egg fuse during fertilization. *

law of segregation

paired unit factors (i.e., genes) segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors

allele

gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes

phenotype

observable traits expressed by an organism

heterozygous (heterozygotes)

having two different alleles for a given gene on the homologous chromosome

dominant

trait which confers the same physical appearance whether an individual has two copies of the trait or one copy of the dominant trait and one copy of the recessive trait

recessive

trait that appears “latent” or non-expressed when the individual also carries a dominant trait for that same characteristic; when present as two identical copies, the recessive trait is expressed

homozygous

having two identical alleles for a given gene on the homologous chromosome

law of independent assortment

genes do not influence each other with regard to sorting of alleles into gametes; every possible combination of alleles is equally likely to occur

dihybrid

result of a cross between two true-breeding parents that express different traits for two characteristics

pedigree

a visual family tree used to trace the inheritance of a specific trait, disease, or allele through multiple generations. *

carriers

a heterozygous individual who possesses one recessive allele for a genetic disorder but does not display the physical symptoms of the trait *

sex-linked genes

genes located on the sex chromosomes *

crossing over

the process where homologous chromosomes pair up and exchange segments of their genetic material *

aneuploidy

condition of a cell having an extra chromosome or missing a chromosome for its species

nondisjunction

failure of synapsed homologs to completely separate and migrate to separate poles during the first cell division of meiosis

deletions

a type of mutation where one or more nucleotides are removed from a DNA sequence, or a segment of a chromosome is lost

duplications

a type of chromosomal mutation where a segment of a chromosome is copied and inserted, resulting in extra genetic material

inversion

soles of the feet moving inward, toward the midline of the body

translocation

process by which one segment of a chromosome dissociates and reattaches to a different, nonhomologous chromosome

down syndrome

a genetic disorder caused by nondisjunction during meiosis.

double helix

the twisted-ladder shape of DNA

antiparallel

the structure of the DNA double helix, where the two complementary strands run in opposite directions.

semiconservative

when a DNA double helix is copied, each of the two resulting DNA molecules is an exact hybrid: it consists of one original (parent) strand and one newly synthesized complementary strand. *

replication fork

Y-shaped structure formed during initiation of replication

DNA polymerase

the primary enzyme responsible for synthesizing new DNA during replication.

DNA replication

the semiconservative process where a cell copies its DNA before division

phage

a type of virus that exclusively infects and replicates inside bacteria

helicase

during replication, this enzyme helps to open up the DNA helix by breaking the hydrogen bonds

primase

enzyme that synthesizes the RNA primer; the primer is needed for DNA pol to start synthesis of a new DNA strand

origin of replication

the specific sequence of DNA where duplication begins

leading strand

strand that is synthesized continuously in the 5'-3' direction which is synthesized in the direction of the replication fork

lagging strand

during replication, the strand that is replicated in short fragments and away from the replication fork

transcription

process through which messenger RNA forms on a template of DNA

translation

process through which RNA directs the formation of protein

messenger RNA (mRNA)

RNA that carries information from DNA to ribosomes during protein synthesis

codon

three consecutive nucleotides in mRNA that specify the insertion of an amino acid or the release of a polypeptide chain during translation

RNA polymerase

the primary enzyme responsible for transcription *

TATA box

conserved promoter sequence in eukaryotes and prokaryotes that helps to establish the initiation site for transcription

transcription factor

protein that binds to the DNA at the promoter or enhancer region and that influences transcription of a gene

5' cap

a methylated guanosine triphosphate (GTP) molecule that is attached to the 5' end of a messenger RNA to protect the end from degradation

poly-A tail

a series of adenine nucleotides that are attached to the 3' end of an mRNA to protect the end from degradation

intron

non–protein-coding intervening sequences that are spliced from mRNA during processing

exon

sequence present in protein-coding mRNA after completion of pre-mRNA splicing

RNA splicing

a post-transcriptional process in eukaryotic cells where non-coding sequences (introns) are removed from pre-mRNA, and the remaining coding sequences (exons) are joined together to form mature mRNA. *

transfer RNA (tRNA)

RNA that carries activated amino acids to the site of protein synthesis on the ribosome

anticodon

three-nucleotide sequence in a tRNA molecule that corresponds to an mRNA codon

operon

collection of genes involved in a pathway that are transcribed together as a single mRNA in prokaryotic cells

repressor

protein that binds to the operator of prokaryotic genes to prevent transcription

differentiation

the process by which unspecialized stem cells become specialized in their structure and function *

cytoplasmic determinants

maternal substances (such as mRNA and proteins) stored in the unfertilized egg.

proto-oncogene

normal gene that when mutated becomes an oncogene

oncogene

mutated version of a normal gene involved in the positive regulation of the cell cycle

tumor suppressor gene

segment of DNA that codes for regulator proteins that prevent the cell from undergoing uncontrolled division

virus

a submicroscopic, non-living infectious agent that acts as an obligate intracellular parasite

capsid

protein coating of the viral core

lytic cycle

type of virus replication in which virions are released through lysis, or bursting, of the cell

lysogenic cycle

type of virus replication in which the viral genome is incorporated into the genome of the host cell

retrovirus

virus with an RNA genome that must be reverse transcribed into DNA before being incorporated into the host cell genome