Chapter 16 Chromosomes, Genes And Proteins Flashcards
Define chromosome:
A length of DNA, found in the nucleus of a cell
It’s contains genetic information in the form of many different genes
Define DNA:
A molecule that contains genetic information, in the form of genes, that controls the properties that are made in the cell
Define gene:
A length of DNA that codes for one protein
Define alleles:
Alternative forms of genes
Define reduction revision:
A term used to describe what happens in meiosis, where the number of chromosomes is halved (reduced)
Define homozygous:
Having two identical alleles of a particular gene
(E.g. GG/gg)
Define heterozygous:
Having 2 different alleles of a particular gene
(E.g. Gg)
Define genotype:
The genetic makeup of an organism in terms of the alleles present
(E.g. GG)
Define phenotype:
The observable features of an organism
Define dominant allele:
And allele that is expressed if it is present
(E.g. G)
Define recessive allele:
An allele that is only expressed when there is no dominant allele of the gene present
(E.g g)
Define codominance:
Alleles that are both expressed in the phenotype when they are both present
Define inheritance:
The transmission of genetic information from generation to generation
Define genetic diagram:
A standard way of showing all the steps in making predictions about the probable genotypes and phenotypes of the offspring from the two parents
Define monohybrid cross:
A cross where we consider the inheritance of only one gene
Define punnet square:
The part of a genetic diagram that shows the predicted genotypes and phenotypes that can result from the random fusion of the male and female gametes
Define test cross:
A cross used to try to determine the genotype of an organism showing the characteristic produced by a dominant allele
The unknown organism is crossed with one showing the recessive characteristic
Define sex chromosomes:
Chromosomes that determine sex
Define X chromosome:
The larger of the 2 sex chromosomes in mammals
Define Y chromosome:
The smaller of the 2 sex chromosomes in mammals
Define sex-linked genes:
Genes that are found on a part of one of the sex chromosomes (usually the X chromosome) and not on the other sex chromosome
They therefore produce characteristics that are more common in one sex than in the other
Define messenger RNA:
(mRNA)
A molecule that carries a copy of the information on DNA to a ribosome, to be used to synthesise a protein 
Define expressed:
Used to make a protein; a gene is expressed when the protein that it codes for is synthesised in a cell
Define stem cells:
Unspecialised cells that are able to divide by mitosis to produce different types of specialised cell
Define mitosis:
A nuclear division which gives rise to genetically identical cells
Define stem cells:
Stem cells are special cells that retain their ability to divide continuously
What is an allele?
A version of a gene
What is homologous chromosomes?
a pair of chromosomes that have the gene coding for the same protein, in the same position
What is monohybrid inheritance?
Monohybrid inheritance is looking at the inheritance of a single characteristic (e.g.,eye colour) which is controlled by only one pair of alleles.
What is meiosis?
Meiosis is a reduction division in which the chromosome number is halved from
diploid to haploid, resulting in genetically different cells.
