Reproduction and inheritance - IGCSE Flashcards
Asexual reproduction
A form of reproduction involving a single parent
It creates genetically identical offspring
Sexual reproduction
A form of reproduction involving the fusion of male and female gametes
It creates genetic variation
Fertilisation
The fusion of the nucleus of male and female gametes
It restores the full chromosome number
Pollination
The transfer of pollen grains (either by the wind or insects) from the male part of a plant to a female part, enabling fertilisation
Embryo
An unborn organism in an early stage of development
Zygote
A fertilised egg
Gametes
Sex cells with half the usual number of chromosomes
Menstrual cycle
The monthly cycle in women that involves the development of the uterus lining, ovulation, maintenance of the uterus lining and its shedding
Luteinising hormone (LH)
A hormone secreted by pituitary gland that initiates ovulation (the release of an egg from the ovary)
Follicle-stimulating hormone (FSH)
A hormone produced by the pituitary gland that stimulates the growth of follicles in the ovary and the secretion of oestrogen
Oestrogen
The main female reproductive hormone released by the ovaries that causes the growth and repair of the uterus lining
Oestrogen is also responsible for the development of secondary sexual characteristics
Progesterone
A hormone produced in the ovaries and placenta that mantains in the uterus lining
Testosterone
The main male reproductive hormone produced by the testes
It stimulates the production of sperm and is responsible for the development of male secondary sexual characteristics
Secondary sexual characteristics
Features that appear during puberty and differ between males and females
DNA
A double-stranded polymer wound to form a double helix that carries the genetic code
Each polymer contains long sequences of four bases: adenine, cytosine, guanine and thymine
RNA
A single-stranded polymer that contains the same bases as DNA, expected that thymine is replaced with uracil
Gene
A section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
Chromosome
A long, coiled molecule of DNA that carries genetic information in the form of genes
Sex chromosomes
A pair of chromosomes that determines the sex of an individual
XX in human females and XY in males
Allele
A version of a gene
Alleles cause differences in inherited characteristics
Genome
The complete genetic material of an organism
Genotype
An organism’s genetic composition
Describes all alleles
Phenotype
An organism’s obsevable characteristics
Due to interactions of the genotype and the environment
Heterozygous
When someone has two different alleles of a gene
Homozygous
When someone has two identical alleles of a gene
Haploid
Refers to a cell that contains one set of chromosomes
Diploid
Refers to a cell that contains two sets of chromosomes
A diploid human cell contains 46 chromosomes
Meiosis
A form of cell division that produces gametes, non-identical cells with half the usual number of chromosomes
Mitosis
A form of cell division that produces two genetically identical daughter cells (with a full set of chromosomes) from one parent cell.
Mitosis is involved in repair, growth, cloning and asexual reproduction
Mutation
A random change in DNA which may result in genetic variants
Protein synthesis
The formation of a protein from a gene
Transcription
The first stage of protein synthesis in which an mRNA molecule is synthesised in the nucleus
It is complementary to a particular sequence of DNA
Recessive
Describes an allele that is only expressed in the absence of a dominant allele
Dominant
Describes an allele that is always expressed
tRNA
A form of RNA that carries specific amino acids to the ribosomes for translation
mRNA
A molecule of RNA that has a complementary sequence to that of a specific DNAA molecule
The mRNA molecule is formed in the nucleus
It leaves and moves to the ribosomes in the cytoplasm
Translation
The second phase of protein synthesis that takes place in the ribosome
mRNA is used as a template for the attachment of tRNA molecules with complementary anticodons
The amino acids carried on adjacent tRNA molecules are joined to form a protein
