Year 12 Biology Unit 4 QCAA

DNA helicase

An enzyme that unwinds the DNA double helix during DNA replication

DNA Replication

The process in which DNA molecules are copied -- produces two identical DNA molecules (must occur before cells divide)

Leading strand

the new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the mandatory 5' to 3' direction

Lagging strand

The strand in replication that is copied 3' to 5' as Okazaki fragments and then joined up.

DNA Polymerase

Enzyme involved in DNA replication that joins individual nucleotides to produce a DNA molecule

Ligase

Enzyme that joins the sugar-phosphate backbones of the Okazaki fragments, forming a signel new DNA strand

A-T and C-G

The complementary base pairs of DNA

Hydrogen bond

The bond between nitrogenous bases of a DNA molecule

Nucleotide

The monomer of DNA - consists of phosphate, deoxyribose sugar, and a nitrogenous base

Nitrogenous bases

Adenine, Thymine, Cytosine, and Guanine are these parts of the nucleotides of DNA; make up the "rungs of the ladder"

Phosphate and Deoxyribose sugar

Parts of the nucleotide that make up the "uprights of the ladder"

DNA

A nucleic acid that contains the genetic information of the cell; shaped as a double helix

Sister chromatids

Replicated forms of a chromosome joined together by the centromere and eventually separated during mitosis or meiosis II.

Centromere

Area where the chromatids of a chromosome are attached

Chromosome

Tightly coiled DNA will produce this. A threadlike, gene-carrying structure found in the nucleus.

Homologous chromosomes

Chromosomes that carry genes controlling the same inherited characters

Centriole

Organelle associated with the centrosome of animal cells only -- assists in cell division

Spindle fibers

Made up of microtubules -- used to pull chromatids apart and chromosomes to opposite sides of the cell

Gene

Segment of DNA; hereditary unit with coded information

Allele

Alternate versions of a gene

Cell Cycle

The regular sequence of growth and division that cells undergo

Somatic Cell

All body cells (except reproductive cells)

Gametes

Reproductive cells (sperm and egg cells)

Interphase

~90% of cell cycle - cell grows and copies its chromosomes in preparate of cell division (consists of G1, S, and G2 phases)

S phase

Part of interphase in which the DNA replication occurs -- all of the chromosom

Mitosis

Division of chromosomes; has 4 stages (PMAT)

Prophase

The first stage of mitosis

Anaphase

The third stage of mitosis: when sister chromatids are pulled apart

Telophase

The fourth stage of mitosis

Metaphase

The second stage of mitosis: when the chromosomes are lined up in the middle

PMAT

The way to remember the steps of mitosis

Cytokinesis

At the end of M Phase --> Division of cytoplasm

Fertilization

The process of a sperm cell uniting with an egg cell

Zygote

The resultant diploid cell after a sperm cell fertilizes an egg cell

Sexual reproduction

Type of reproduction where the combination of genetic information from two separate parents produces offspring = leads to genetic diversity in a population

Autosomes

All the chromosomes in our cells other than the X and Y chromosome (the 1st through the 22nd chromosomes shown on a karyotype)

Sex chromosomes

X and Y chromosomes in human cells (the 23rd chromosomes on a karyotype)

Dipolid cell

Cells that contain 2 of each chromosomes - ex: human skin cell has 23 pairs of homologous chromosomes

Haploid cell

Cells that contain only 1 of each chromosome - OR HALF the amount of chromosomes - ex: human sperm cell has 23 chromosomes

Meiosis

2 Cell divisions that produces 4 haploid daughter cells that become either sperm, if performed in the testes of a male, or egg, if performed in the ovaries of a female

Crossing over

Event that occurs in Prophase I of Meiosis I where homologous chromosomes that are paired up exchange equal segments (genes) with each other -- leads to genetic variation in offspring

Nondisjuction

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

Asexual reproduction

Type of reproduction where offspring are produced from one parent; those offspring are genetically identical to the parent

independent assortment

Independent segregation of genes during the formation of gametes

Gametogenesis

Gamete production. Spermatogenesis and Oogenesis

DNA primer

A small piece of single-stranded DNA. It acts a signal, binding to and marking the piece of DNA which is to be copied.

Spermatogenesis

production of sperm

Oogenesis

the production, growth, and maturation of an egg, or ovum

polar bodies

each of the small cells that bud off from an oocyte at the two meiotic divisions and do not develop into ova.

spermatozoon

sperm cell

genetic recombination

new combination of genes produced by crossing over and independent assortment

Genome

the complete set of nucleotide sequences encoded in the total DNA of an organism

structural genes

sections of DNA that carry the instructions for production of a protein

gene expression

process by which a gene produces its product and the product carries out its function

Non-coding DNA

the greater part of the DNA molecule that does not contain structural genes. Do not code for specific proteins.

regulatory gene

a non-coding segment of DNA that produces

transcription factors for gene expression

mRNA

messenger RNA; type of RNA that carries instructions from DNA in the nucleus to the ribosome

DNA transcription

the formation of an RNA strand complementary to the DNA strand by RNA polymerase

Codon

three-nucleotide sequence on messenger RNA that codes for a single amino acid

Split genes

genes with intervening sequences of introns and exons

Intron

sequence of DNA that is not involved in coding for a protein

Exon

a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.

trimming

removal of non-coding sections at the beginning and end of mRNA

tRNA

transfer RNA; type of RNA that carries amino acids to the ribosome

Anticodon

group of three bases on a tRNA molecule that are complementary to an mRNA codon

rRNA

Ribosomal RNA

polysome

A complex formed when multiple ribosomes are translating the same mRNA into proteins.

Translation

Process by which mRNA is decoded and a protein is produced

transcription factors

A regulatory protein that binds to DNA and affects transcription of specific genes.

Epigenetics

the study of environmental influences on gene expression that occur without a DNA change

Hox genes

a sub-group of homeotic genes that control the body plan of an embryo along the head-tail axis

cell differentiation

the process by which a cell becomes specialized for a specific structure or function.

sex determination

The biological mechanism that determines whether an organism will develop as a male or female

repressor protein

a regulatory protein that binds to an operator and blocks transcription of the genes of an operon

SYR gene

sex determining region of the Y chromosome

histone modification

changes in the structure of histones that make it more or less likely that a segment of DNA will be transcribed

monozygotic twins

twins who are genetically identical

Mutation

small permanent change in the DNA of an organism

point mutation

a change in a single nucleotide in the DNA code that may result in translation of one different amino acid in a polypeptide sequence

frameshift mutation

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

Non-disjunction

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

Aneuploidy

the presence of an abnormal number of chromosomes in a cell

Karotype

A picture of all the chromosomes in a cell arranged in pairs

Ploidy

number of sets of chromosomes in a cell

Trisomy

3 copies of a chromosome

Mutagens

A chemical or physical agent that interacts with DNA and causes a mutation.

Homozygous

An organism that has two identical alleles for a trait

pure breeding

Individuals that are homozygous that will always produce the same offspring when crossed together

Heterozygous

An organism that has two different alleles for a trait

dominant trait

A genetic trait is considered dominant if it is expressed in a person who has only one copy of the gene associated with the trait.

recessive allele

An allele that is masked when a dominant allele is present

Genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits.

Punnett Square

A chart that shows all the possible combinations of alleles that can result from a genetic cross

monoybrid cross

genetic cross between two individuals investigating only one specific trait

dihybrid cross

Cross or mating between organisms involving two pairs of contrasting traits

frequency histogram

type of bar graph that shows frequency distributions

Codominance

A condition in which both alleles for a gene are fully expressed

incomplete dominance

A pattern of inheritance in which two alleles, inherited from the parents, are neither dominant nor recessive. The resulting offspring have a phenotype that is a blending of the parental traits.

Multiple or poly alleles

the inheritance of a characteristic governed by more than two allelic forms forms. E.g. blood groups