bio chap 21 genetic inheritance

nucleotides

DNA is made up of repeating units called…

double helix

nucleotides linked together in two long strands that wing around each other to form…

nucleotides have components:

• phosphate group

• five-carbon sugar called deoxyribose

• one of four different nitrogenous bases

nitrogenous bases

adenine (A), guanine (G), cytosine (C), and thymine (T)

Adenine (A) pairs with

thymine (T)

guanine (G) pairs with

cytosine (C)

father of genetics

gregor mendel

hereditary factors (genes)

passed from one generation to the next

different factors of genes

dominant and recessive

genetics

study of inherited traits which are controlled by hereditary factors called genes

human genome

23 pairs (or 46) chromosomes; 20,000-25,000 different genes

homologous pairs of chromosomes

two chromosomes (one paternal one maternal), that are identical in appearance and pair during meiosis

genes

segments of DNA; code for a specific protein that will play a structural or functional role in the cell

genetic trait

specific characteristic of an individual that is determined by genes, environmental factors, or both

two letters

are used when representing the genes of an organism

homozygous

inheriting the same version of a gene from both parents (eg; two genes for blonde hair)

heterozygous

inheriting different version of a gene from each parent (blonde gene and brunette gene)

genotype

genetic composition of an individual

phenotype

observable physical traits of an individual

law of dominance

if the two alleles for a trait differ, then one, the dominant allele, determines the organisms appearance; the recessive allele sometimes has no noticeable effect

dominant allele (“A”)

expressed even if theres only one copy

recessive allele (“a”)

only be expressed if there are two copies

freckled phenotype

two genotypes: FF and Ff

polygenic inheritance

variation in a trait that involves two or more genes; vary almost continuously from one extreme to another (height, skin, eye color)

autosomal recessive inhereitance

both genders; homozygotes are affected (aa), heterozygotes are carriers (Aa); can skip generations ; sickle cell, cystic fibrosis, tay-sachs disease

sickle cell anemia

recessive; resistance to malaria

cystic fibrosis

recessive

autosomal dominant inheritance

both genders; if child has trait, at least one parent has trait; does not skip generations (if no offspring inherited trait, its transmission stops)

achondroplasia (autosomal dominant)

genetic condition affecting a protein called fibroblast growth factor receptor; Aa affected, aa unaffected, AA never born