Module 5: Heredity

Reproduction

the process of producing offspring

Asexual reproduction

A reproductive process that involves only one parent and produces offspring that are identical to the parent.

Sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism, which differs from both parents

Fertilisation

Process in sexual reproduction in which male and female reproductive cells join to form a new cell

Implantation

Process in which the blastocyst attaches to the wall of the uterus

Pollination

The transfer of pollen from male reproductive structures to female reproductive structures in plants

Binary Fission

A form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size

Replication

Copying process by which a cell duplicates its DNA (prior to cell division)

Meiosis

A type of cell division that results in four daughter cells each genetically unique, with half the number of chromosomes of the parent cell, as in the production of gametes and plant spores.

Cytokinesis

Division of the cytoplasm to form two separate daughter cells

Chromosomes

Threadlike structures of nucleic acids (DNA) wrapped with histone proteins found in the nucleus of most living cells, carrying genetic information in the form of genes (that codes the inherited characteristics of an organism).

Chromatid

one (of two) copies of a newly copied chromosome (formed during interphase) that is still joined to the other copy by a single centromere

Homologous chromosomes (homologs)

A matching pair of chromosomes in a diploid organism (2 chromosomes and 4 chromatids), with one coming from each parent. They carry the same genes in the same loci.

Pedigree

A diagram that shows the occurrence and pattern of inheritance of a particular genetic trait over several generations of a family.

Genotype

The combination of alleles for a trait carried by an individual, or the total set of genes of an organism.

Phenotype

An observable trait. The expression of a genotype of an individual for a particular trait.
Dominance of alleles and environmental conditions influence this.

Dominant allele

An allele whose trait always shows up in the organism's phenotype when the allele is present.

Recessive allele

An allele whose phenotypic effect is not observed when a dominant allele is present (in a heterozygote).

Homozygous

An organism that has two identical alleles for a particular gene.

Heterozygous

An organism that has two different alleles for a particular gene.

Polymorphism

occurrence of different allelic forms of a gene in a population

DNA Sequencing

determining the exact order of nucleotide bases in a gene or segment of DNA

Nucleotide

Basic units (monomers) of nucleic acids - DNA or RNA molecule. Composed of a *5-carbon sugar (ribose in RNA, deoxyribose in DNA), a *phosphate group, and a nitrogenous base (purine or pyrimidine). 4 types in DNA - adenine (A), thymine (T), guanine (G) and cytosine (C) or RNA base uracil (U).

Polypeptide synthesis

involves two major steps; transcription (DNA generates mRNA copy) and translation (mRNA used to synthesise a chain of amino acids).

Parthenogenesis

Reproduction from an ovum without fertilisation, especially as a normal process in some invertebrates and lower plants.

DNA (deoxyribonucleic acid)

A double stranded nucleic acid that contains the genetic code in its sequence of bases. It is the instructions for life. It is found in all organisms, in chromosomes, as well as mitochondria and chloroplasts.

Polypeptide

A polymer (chain) of many amino acids linked together by peptide bonds.

Protein

An organic compound that is made of one or more chains of amino acids (polypeptides) and has a distinct and varied 3D structure, and a principal component of cells.

Ribosome

site of protein synthesis

DNA polymerase

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

Allele

One of a number of different forms of a gene

Autosomal inheritance

Inheritance of a genetic trait not on a sex chromosome

Sex-linked inheritance (sex-linkage)

Inheritance of traits by genes located on either sex chromosome (X or Y)

Co-dominance

A situation in which both inherited alleles of a gene contribute to the phenotype of the organism (both are expressed). Neither is dominant over the other.
e.g. roan coat colour in cattle.

Incomplete dominance

A form of inheritance in which neither the dominant or recessive phenotype is expressed completely. In heterozygotes, both alleles are partially expressed, producing an intermediate phenotype (a blending of parental traits).
e.g. colour of snapdragon flowers (mix red and white to produce pink)

Multiple allele inheritance

Inheritance pattern in which there are more than 2 alleles influencing/for a particular trait; and each individual has only 2 of all possible alleles. (example=blood type)

A punnet square shows

All the possible genotypic outcomes of a genetic cross between two sets of parental alleles.

Single Nucleotide Polymorphism (SNP)

A single base-pair difference/variation in DNA, used for genome comparison and studies of the association between genes.

DNA profiling (DNA fingerprinting)

A procedure that generates a genetic pattern unique to an individual, by amplifying multiple genetic markers (DNA fragments), called Short Tandem Repeats (STRs) and using to compare with others to establish identity to determine whether they come from a specific individual. (Also known as a DNA fingerprint).

Inheritance

The process in which genetic material (and thus characteristics) are passed from parents to their offspring.

Population genetics

A field of scientific study concerned with genetic differences within and between populations.

Mitosis

A division of the nucleus (of somatic cells) that results in two cells that are genetically identical to the parent cell. eg. asexual reproduction and cell replication for growth occur by mitosis.

Heredity

The inheritance of a set of genetic characteristics from a combination of parental DNA.

Haploid

(genetics) an organism or cell having only one complete set of chromosomes

Diploid

(genetics) an organism or cell having two sets of chromosomes or twice the haploid number

Gamete

sex cell

Organ of perennation

a plant organ that stores food

Conjugation

A temporary union of bacteria for the purpose of DNA transfer.

Spores

Asexual reproductive or resting cell capable of developing into a new organism without fusion with another cell, in contrast to a gamete

Sporangium

spore capsule in which haploid spores are produced by meiosis