Year 12 Biology Unit 4 Topic 1 Genetics (QCAA - from quizlet)

Hydrogen bond

The type of bond between nitrogenous bases of a DNA molecule

Asexual reproduction

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

genetic recombination

This process occurs when genetic material is exchanged between chromosomes (ie. crossing over) and a new combination of genes is produced

genome

All the genetic material in the chromosomes of an organism, including its genes and DNA sequences

gene expression

The process in which the instructions encoded in DNA direct the production of a functional product, such as a protein or RNA molecules.

regulatory gene

a non-coding segment of DNA that produces transcription factors for gene expression

Transcription factor

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

Epigenetics

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

microRNA

A small, noncoding RNA molecule that regulates gene expression by binding to mRNA to inhibit its translation.

Heterozygous

An organism that has two different alleles for a trait

Frequency histogram

Type of bar graph that shows frequency distributions

Codominance

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

Primer

A short segment of DNA that acts as the starting point for a new strand

DNA Ligase

Enzyme that joins the ends of cut DNA strands according to the complementary base-paring rule

Restriction enzyme (endonucleases)

An enzyme specialised for 'cutting' a DNA strand which features a specific nucleotide sequence that is used to identify and isolate a target piece of DNA.

polymerase chain reaction (PCR)

A method of producing thousands of copies of DNA segment using the enzyme DNA polymerase.

DNA

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

Nitrogenous bases

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

DNA Replication

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

Chromosome

A threadlike, gene-carrying structure found in the nucleus. Consists of tightly coiled DNA.

DNA helicase

An enzyme that unwinds the DNA double helix during DNA replication

Leading strand

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

DNA Polymerase

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

Centromere

Area where the chromatids of a chromosome are attached

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 fibres

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

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

The stage of the cell cycle when the cell grows and replicates its chromosomes in preparation for cell division (consists of G1, S, and G2 phases)

Mitosis

Process of cell division that produces 2 identical daughter cells; has 4 stages (PMAT); involved in growth and repair.

Anaphase

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

Cytokinesis

Division of cytoplasm to form two daughter cells

Zygote

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

Sex chromosomes

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

Dipolid cell

Cells that contain 2 of each chromosomes - eg: human skin cell has 23 pairs of homologous chromosomes (a full set)

Meiosis

Two cell divisions that produces four 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

Independent assortment

Process by which the paternal and maternal chromosomes of each homologous pair line up independently of the other pairs as they separate in meiosis - so chromosomes are randomly assorted into gametes

Spermatogenesis

Production of sperm

Oogenesis

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

Non-coding DNA

Parts of the DNA molecule (between or within genes) that does not code for specific proteins.

mRNA

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

Codon

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

Telomeres

Repeating segments at the ends of chromosomes that do not form genes and help prevent the loss of genes over time

mRNA splicing

Removal of non-coding sections in a strand of pre-mRNA

Anticodon

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

rRNA

ribosomal RNA; makes up the ribosomes

Translation

Process by which mRNA is decoded and a protein is produced

HOX genes

A sub-group of homeobox genes in animals that control the body plan of an embryo along the head-tail axis

activator protein

A regulatory protein that increases the transcription of a gene (ie. 'switches it on')

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

Mutation

A change in a gene or a chromosome relative to the original; may be spontaneous or induced

point mutation

A type of mutation resulting from 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

Aneuploidy

The presence of an abnormal number of chromosomes in a cell

Karyotype

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 (instead of 2)

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

dominant

Describes a trait that covers over, or dominates, another form of that trait. Will be expressed when only one copy of the allele is present.

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

dihybrid cross

A genetic cross between organisms involving two different traits

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 allele inheritance

The inheritance of a characteristic governed by more than two types of alleles, e.g. blood groups (ABO)

X-linked (or sex-linked)

A trait controlled by a gene on the X chromosome

continuous variation

Variation (along a continuum) in a phenotype as a result of more than one gene contributing to a characteristic

Carrier

A person whose genotype includes a gene that is not expressed in the phenotype.

Recombinant DNA

DNA produced by combining DNA from different organisms

Taq Polymerase

A heat-stable form of DNA polymerase extracted from bacteria that live in hot environments, such as hot springs, that is used during PCR technique

DNA sequencing

The process of determining the precise order of nucleotides within a DNA molecule.

DNA profiling

A procedure that analyses Short Tandem Repeats (STRs) of DNA fragments to determine whether they come from a specific individual. Use for paternity testing and forensics.

A-T, C-G (adenine, thymine, cytosine, guanine)

The complementary base pairs of DNA

Nucleotide

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

Phosphate and Deoxyribose sugar

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

Lagging strand

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

Ligase

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

Sister chromatids

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

Gene

Section of DNA; hereditary unit with coded information

Allele

Alternate versions of a gene

Prophase

The first stage of mitosis when chromosomes condense.

Metaphase

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

Telophase

The fourth stage of mitosis

PMAT

The way to remember the steps of mitosis

Fertilisation

The process of a sperm cell uniting with an egg cell

Sexual reproduction

Type of reproduction where the combination of gametes 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 sex chromosome (chromosome pairs 1-22 in a karyotype)

Haploid cell

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

Crossing over

An event during meiosis in which homologous chromosomes pair up and exchange DNA segments with one another -- increases genetic variation in offspring

Gametogenesis

General name for gamete production, either spermatogenesis or 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.

Polar bodies

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

Structural genes

Sections of DNA that code for any RNA or protein product except regulatory factors (eg. transcription factors).

Transcription

Process in which an mRNA strand is built by the enzyme RNA polymerase (complementary to the DNA strand)

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.