Genetics Flashcards
gregor mendel
bred garden peas, argued that parents pass on to their offspring discrete heritable factors, said genes retain their individuality generation after generation (don’t blend). true bred plants
hypotheses:
1. there are alternative versions of genes that account for variations in inherited characters, alternative versions of genes called alleles
2. for each character, an organism inherits two alleles, one from each parent. can be homogenous or heterozygous
3. if the two alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele; the other has no noticeable effect on the organism’s appearance and is called the recessive allele
4. a sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes
true-breeding
varieties of an organism for which self-fertilization produces offspring identical to the parent
hybrid
the offspring of two different varieties of organism (ex. purple plant bred with white plant, offspring is hybrid)
fertilization
the union of the nucleus of a sperm cell with the nucleus of an egg cell, producing a zygote. organisms fertilize one another to make more
p generation
first generation, parents, true-breeding
f1 generation
hybrid offspring of p generation
f2 generation
when f1 plants self fertilize or fertilize one another, offspring are f2 generation
monohybrid cross
when two parents are mated that only have one different character
dihybrid cross
a mating of parental varieties differing in two characters
gene
factors that parents pass on to their children. they remain individuality generation after generation. they determine certain characteristics of the children
allele
the alternative versions of a gene. different alleles count for variations in inherited characteristics
genotype
an organism’s genetic makeup (ex. Gg)
phenotype
an organism’s expressed, or physical, traits (ex. white flowers)
recessive
the allele that has no noticeable effect on the organism’s appearance. if a gene is recessive, it may skip generations. the only time it is expressed is it the person has two recessive alleles, lower case
dominant
the allele that determines the organism’s appearance, upper case
heterozygous
an organism that has two different alleles for a gene is heterozygous for that gene and is called a heterozygote
homozygous
an organism that has two identical alleles for a gene is homozygous for that gene and is called a homozygote
law of segregation
one of mendel’s laws. a sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes
law of independent assortment
one of mendel’s, each pair of alleles segregates independently of other pairs of alleles during gamete formation
gametes
a sex cell; a haploid egg or sperm. the union of two gametes of opposite sex produces a zygote
locus
the particular site where a gene is found on a chromosome. homologous chromosomes have corresponding gene loci. alleles of a gene reside at the same locus on homologous chromosomes
homologous chromosomes
homologues, chromosomes that carry genes controlling the same inherited characteristics. homologous chromosomes have genes for the same characters located at the same positions along their lengths
amniocentesis
needle into uterus, take out fetus cells, allows for karyotyping
CVS
chorionic villus sampling, biochemical testing
mendelian genetics
explain inheritance in terms of discrete factors (genes) that are passed on along from generation to generation according to simple rules of probability. valid for all sexually producing organisms but often don’t cover it all
non mendelian genetics
codominance, incomplete dominance, pleiotropy, polygenic
incomplete dominance
when the appearance of f1 hybrids falls between the phenotypes of the two parental varieties (ex. red and white flowers make pink flowers. NOT BLENDING
codominance
both alleles are expressed in heterozygous individuals (ex. blood types)
pleiotropy
when genes influence multiple characters
SICKLE CELL ANEMIA
most genes
polygenic inheritance
the additive effects of two or more genes on a single phenotypic character. converse of pleiotropy. multiple letters (ex. skin color = AABbcc
linked genes
genes located close together on the same chromosome tend to be inherited together and are called linked genes. generally do not follow mender’s law of independent assortment
WEIRD RATIO = LINKED GENE
chromosome theory of inheritance
cells undergoing meiosis. genes occupy specific loci on chromosomes and it is the chromosomes that undergo segregation and independent assortment during meiosis. thus, it is the behavior of chromosomes during meiosis and fertilization that accounts for inheritance patterns
crossing over
recombines linked genes into mixtures of alleles not found in parents
chromosomes of offspring have combo that neither parent has
creates gamete diversity
recombinants
recombinant gametes are gametes that are made from a recombination of parental genes (ex. by crossing over)
sex chromosome
X and Y
sex-linked traits
a gene located on either sex chromosome is a sex-linked gene. traits that are sex-linked are passed on with the sex chromosomes
pedigree
a family tree representing the occurrence of heritable traits in parents and offspring across a number of generations
autosomal recessive
not sex-linked, two copies of recessive gene given to child, skips generations
autosomal dominant
not sex-linked, at least one dominant gene, stays generations
chi-square
X^2 = Σ[(O-E)^2/E]
Take observed minus expected squared divided by expected and then add all those together
