Bio Test 5

nucleic acid

a polymer consisting of many nucleotide monomers that serves as a blueprint for proteins and, through the actions of proteins, for all cellular structures and activites

transcription

the synthesis of RNA on a DNA template

haploid

a cell containing a single set of chromosomes (an n cell)

double helix

the form of DNA where two adjacent polynucleotide strands wind into a spiral

translation

the synthesis of a polypeptide using the genetic information encoded in a mRNA molecule. there is a change of ‘language’ from nucleotides to amino acids

diploid

a cell containing two homologous sets of chromosomes with one set inherited from each parent (a 2n cell)

codon

DNA and RNA sequences that are a series of non-overlapping, 3 base “words”

crossing over

the exchange of segments between chromatids of homologous chromosomes during synapsis in prophase I of meiosis

sugar-phosphate backbone

the alternating chain of sugar and phosphate to which nitrogenous bases are attached in DNA or RNA

germ cell

a diploid cell that produces gametes

deoxyribose

the sugar used in DNA

polypeptide

a polymer (chain) of amino acids linked by peptide bonds

somatic cell

a diploid body cell

nucleotide

a five-carbon sugar covalently bonded to a nitrogenous base and one or more phosphate groups, building block of nucleic acids

gametic cell

a sex cell, a haploid egg or sperm, the union of two of them produces a zygote

cell plate

a double membrane across the midline of a dividing pant cell, beteween which the new cell wall storms during cytokinesis

autosome

one of the 22 chromosomes not involved in determining sex

chromosome

a gene-carrying structure found in the nucleus of a eukaryotic cell and most visible during mitosis and meiosis, consists of one very long DNA molecule and associated proteins

Law of Independent Assortment

general rule of inheritance (from Mendel) that says when gametes form during meiosis, each pair of alleles for a particular character segregates independently of each other

karyotype

a displace of micrographs of the metaphase chromosomes of a cell, arranged by size and centromere position, may be used to identify certain chromosomal abnormalities

chromatin

the complex of DNA and proteins that makes up eukaryotic chromosomes, often refers to the very extended form taken by chromosomes when a cell is not dividing

Law of Segregation

Mendel’s first law of inheritance, says that individuals have two alleles for each gene and that when gametes form by meiosis, the two alleles separate, each resulting gamete ending up with only one allele of each gene

monosomy

when one of the chromosomes from a pair is missing

chromatid

a single strand of a duplicated chromosome that is connected to its sister chromatid at the centromere.

substitution mutation

LATER

trisomy

when an individual has more than two chromosomes instead of a pair

centromere

the region of a duplicated chromosome where two sister chromatids are joined and where spindle microtubules attach during mitosis and meiosis, divides at the onset of anaphase during mitosis and anaphase II during meiosis

missense mutation

a change in the nucleotide sequence of a gene that alters the amino acid sequence of the resulting polypeptide. in a missense mutation, a codon is changed from encoding one amino acid to encoding a different amino acid

deletion

the loss of one or more nucleotides from a gene by mutation; the loss of a fragment of a chromosome

complementary base pair

LATER

nonsense mutation

a change in the nucleotide sequence of a gene that converts an amino-acid-encoding codon to a stop codon, results in a shortened polypeptide

insertion

LATER

spindle fiber

a structure made of microtubules that is involved in the movement of chromosomes during mitosis and meiosis

silent mutation

a mutation that changes a codon to one that codes for the same amino acid as the original codon, the amino acid sequence of the resulting polypeptide is thus unchanged

translocation

reciprocal translocation when segments from two different have been exchanged; robertsonian translocation when an entire chromosome has attached to another at the centromere

homologous

two chromosomes that make up a matched pair in a diploid cell, of the same length, centromere position, and staining pattern and possess genes for the same characters at corresponding loci, one is inherited from the father and one from the mother

frameshift mutation

a change in the genetic material that involves the insertion or deletion of one or more nucleotides in a gene, resulting in a change in the triplet grouping nucleotides

inversion

a change in a chromosome resulting from reattachment of a chromosome fragment to the original chromosome, but in the reverse direction, mutagens and errors during meiosis can cause inversions

tetrad

LATER

telomere

a region of repetitive DNA sequences at the end of a chromosome, protects the ends of chromosomes from becoming frayed or tangled

cytokinesis

the division of the cytoplasm to form two separate daughter cells, usually occurs in conjunction with telophase of mitosis, mitosis and cytokinesis make up the mitotic (M) phase of the cell cycle

nondisjunction

an accident of meiosis or mitosis in which a pair of homologous chromosomes or a pair of sister chromatids fail to separate at anaphase

histone

a small protein molecule important in DNA packing in the eukaryotic chromosome, eukaryotic chromatin consists of roughly equal parts of DNA and histone protein

gene

a unit of hereditary information consisting of a specific nucleotide sequence in DNA, most of the genes of a eukaryote are located in its chromosomal DNA and a few are carried by the DNA of mitochondria and chloroplasts

genotype

the genetic makeup of an organism

nucleosome

the bead-like unit of DNA packing in a eukaryotic cell, consists of DNA wound twice around a protein core made up of eight histone molecules

allele

an alternative version of a gene

phenotype

the expressed traits of an organism

homozygous

having two identical alleles for a given gene

heterozygous

having two different alleles for a given gene

hybrid

an offspring of two parents that differ in one or more inherited traits, an individual that is heterozygous for one or more pairs of genes

testcross

the mating between an individual of unknown genotype for a particular character and an individual that is homozygous recessive for that same character

pedigree

a family genetic tree representing the occurrence of heritable traits in parents and offspring across a number of generations, can be used to determine genotypes of matings that have already occurred

checkpoints

LATER

interphase

the period in the eukaryotic cell cycle when the cell ins not actually dividing, constitutes the majority of the time spent in the cell cycle

metaphase

the third stage of mitosis, during which all the cell’s duplicated chromosomes are lined up at an imaginary plane equidistant between the poles of the mitotic spindle

prophase

the first stage of mitosis, during which the chromatin condenses to form structures (sister chromatids) visible with a light microscope and the mitotic spindle begins to form, but the nucleus is still intact

anaphase

the fourth stage of mitosis, beginning when sister chromatids separate from each other and ending when a complete set of daughter chromosomes arrives at each of the two poles of the cell

telophase

the fifth and final stage of mitosis, during which daughter nuclei form at the two poles of a cell, usually occurs together with cytokinesis