Chapter 3.4 Flashcards
Chromosomes
Strands of hereditary material
Genes
Sections along each chromosome, control the chemical reactions that direct development.
Dominat
That is, a single copy of the gene is sufficient to produce its effect.
Recessive
Its effects appear only if the dominant gene is absent.
X chromosomes
A female has 2 X chromosomes in each cell, A male has one and a Y chromosome.
Y Chromosome
is one of two sex chromosomes (allosomes) in mammals, including humans, and many other animals. The other is the X chromosome. Y is the sex-determining chromosome in many species, since it is the presence or absence of Y that determines male or female sex.
Sex-linked Genes
Genes located on the x or y chromosome. A recessive gene on the x chromosome shows its effects more in men than in women.
Sex-limited Gene
Occurs equally in both sexes but exerts its effects mainly or entirely in one or the other. For example men and and women have gens for facial hair, but men’s hormones activate those genes.
Epigenetics
Deals with changes in gene expression as a result of environmental influences, without modification of the DNA sequence
Heritability
An estimate of the variance within a population that is due to heredity.
Monozygotic Twins
Develop from a single fertilized egg and therefore have identical gens.
Dizygotic Twins
Develop from two eggs and share only half their genes. (often called fraternal)
Multiplier Effect
A small initial advantage in some behavior, possibly genetic in origin, alters the environment and magnifies that advantage.
Phenylketonuria (PKU)
An inherited condition that, if untreated, leads to mental retardation. ( This makes it so the body can’t metabolize phenylalanine.
Evolution
A gradual change in the frequency of various genes from on generation to the next.
