Chapter 2 Flashcards
Chromosomes
Most cells of the body have a full set of 46 chromosomes- tiny structures in the nucleus that contain genetic material. The gametes each have half that number- 23 chromosomes.
In vitro fertilization (IVF)
In vitro fertilization (IVF), involves mixing sperm and egg together in a laboratory dish and then placing a few of these eggs in the mother’s uterus.
Autosomes
The first 22 pairs of chromosomes are called autosomes, the chromosomes in each pair are about the same size.
Sex chromosome
The 23rd pair determines the sex of the child, these two are know as the sex chromosome. The chromosome labelled X is much larger than the chromosome labelled Y.
Deoxyribonucleic acid (DNA)
Each chromosome actually consists of one molecule of DNA.
Gene
Each group of nucleotide bases that provides a specific set of biochemical instructions is called a gene.
Genotype
The complete set of genes makes up a person’s heredity and is known as a person’s genotype.
Phenotype
Genetic instructions, in conjunction with environmental influences, produce a phenotype, an individual’s physical, behavioural,and physical features.
Alleles
Genes come in different forms which are known as alleles.
Homozygous/ Heterozygous
Sometimes the alleles in the pair of chromosomes are the same, which makes then homozygous. Sometimes the alleles differ, which makes then heterozygous.
Dominant/ Recessive alleles
Often one allele is dominant, which means that its chemical instructions are followed, whereas the instructions of the other, the recessive allele, are ignored.
Incomplete dominance
Sometimes one allele does not dominate another completely, a situation known as incomplete dominance. The phenotype that results often falls in between the phenotype associated with either allele.
Sickle-cell trait
Individuals with one dominant and one recessive sickle cell allele have sickle-cell trait. In most situations they have no problems, but when they are seriously short of oxygen they suffer a temporary, relatively mild form of the disease.
Huntington’s disease
Is a fatal disease characterized by progressive degeneration of the nervous system. Individuals who inherit do not show signs until adulthood making it difficult to detect. Cause by a dominant allele found on chromosome 4.
Hemophilia
A disorder in which the blood does not clot easily and suffered can bleed severely with even minor injury,the gene is carried on the X chromosome.
Down Syndrome
A genetic disorder that is caused by an extra 21 chromosome and results in intellectual disability.
Behavioural genetics
Behavioural genetics is a branch of genetics that deals with inheritance of behavioural and psychological traits.
Polygenic inheritance
Phenotypes often reflect the combined activity of many separate genes.
Monozygotic twins
Identical twins are called monozygotic twins because they come from a single fertilized egg that splits in two.
Dizygotic twins
Fraternal or dizygotic twins come from two separate eggs fertilized by two separate sperm.
Reaction range
The range of phenotypes that the same genotype may produce in reaction to the environment where development takes place.
Epigenesis
The continuous interplay between genes and multiple levels of the environment (from cells to culture) that drives development
Methylation
Sometimes experiences change the expression of DNA. This process is known as methylation because the chemical silencer is a methyl molecule.
Heritability coefficient
Estimates the extent to which differences between people reflect heritability.
Niche-picking
The process of deliberately seeking environments that fit ones heredity is called niche-picking.
Nonshared environmental influences
The environmental differences that make twins different.
