Lecture 1 Flashcards
pre-formationists
ovists (full-ass baby in the egg) vs. animaculists (full-ass baby in sperm)
One sex fully responsible for offspring. Founded by Von Leeuwenhoek in 18th century.
blending inheritance
Inheritance in which no component is obtrusive– blending of characteristics from both egg and sperm. (19th century)
KEY COMPONENT– you can never produce an offspring with similar phenotypes to parents
Law of Segregation
ONLY APPLIES TO ALLELIC STATE OF A SINGLE GENE
only one allele from each parent is assigned to the gamete
Three Components of Mendel’s system
1) Homozygosity of alleles controlling phenotype of interest
2) Paternity must be controlled and known
3) All genotypes should be equally fertile
gene
any sequence of nucleotides in a genome that encodes for a functional RNA
gene locus
position of the nucleotides for a specific gene on a chromosome
allele
one or more alternate forms of a gene that can exist at a single gene locus for a single gene
dominant allele
expresses its phenotypic effect in a heterozygote
- A haploid organism only has one copy of every gene so it is neither homozygous or heterozygous.*
- An allele is neither dominant nor recessive if the heterozygote looks different from either homozygote.*
wild-type
genotype or phenotype most commonly found in nature OR a lab
Law of Independent Assortment
This law states that for each allelic pair of multiple genes (on separate chromosomes!!), segregation is independent for each gene during the formation of gametes.
i.e. One gene’s separation does not impact another one (they are not linked!!)
Forward Genetics
Genes are first identified by mutant alleles and mutant phenotypes and later cloned and subjected to molecular analysis.
biological process -> mutant phenotype -> gene
Reverse Genetics
Begins with cloned DNA segment or protein amino acid sequence and uses directed mutagenesis to introduce altered genes back into the genome to investigate function.
gene–>phenotype–>biological process
CRISPR
Simple dominance
an allele is dominant if it has the same phenotypic effect in heterozygotes and homozygotes
haplosufficient
in a diploid cell, an allele that can promote wild-type function with only one copy (common case)
+/a is sufficient to produce wild-type function
haploinsufficient
in a diploid cell, an allele that cannot promote wild-type function with only one copy (rare)–often tied to dominant mutations
a null (amorphic) allele produces no normal RNA or protein product– can be deadly
mutation
permanent change in DNA that makes up a gene
range in size from a single nucleotide to entire sets of chromosome
De novo mutations
Not inherited mutations– occur just after fertilization, no family history
Can still get passed down because they occur only in an egg or sperm cell
germline mutation
inherited and occur in testes and ovaries, will be passed on to children
All cells affected in offspring
somatic mutation
occur in body cells– not inherited but could still affect the person during their lifetime
Cancer is a somatic mutation
Chromosomal Theory of Inheritance
chromosomes are the vehicles of genetic heredity. Neither Mendelian genetics nor gene linkage is perfectly accurate; instead, chromosome behavior involves segregation, independent assortment, and occasionally, linkage.
chromosome
typically, a linear double-stranded DNA molecule complexed with proteins that moves as an independent unit during mitosis and meiosis.
sister chromatids
One of two visibly distinct, side-by-side and genetically identical copies of a replicated chromosome. Joined at their centromeres.
centromere
A chromosomal locus that regulates chromosome movement during mitosis and meiosis. Sister chromatids are joined together by a common centromere.
kinetichore
A specialized structure that forms at the centromere. It links chromatids to the spindle microtubules
homologous chromosomes
- contain the same arrangement of genes
- identical in visible structure
- pair during meosis I
- In nature, not usually identical but typically exhibit allelic differences (maternal & paternal)
- CAN ALSO REFER TO– Chromosomes in different species that have retained most of the same genes during their evolution from a common ancestor*
Theodor Boveri linked ____ and ______ for the first time.
chromosomes and heredity.
Saw segregation for the first time
sex chromosome
presence or absence is correlated with the sex of the organism, plays role in sex determination
autosome
any chromosome not a sex chromosome
Trisomy X
XXX, does not seem to impact fertility
Klinefelter
XXY, male
in humans, SRY gene determines male (on the Y chromosome)
Turner
XO, female, no Y chromosome to hold the SRY gene
In drosophila, the XO fly is a ____.
sterile male. In flies, Y chromosome is not involved in sex determination but it is required for male sexual function.
hemizygous
biological sexes with 2 different chromosomes, ex. males are X,Y for humans
males more likely to show mutant phenotype
nondisjunction
when homologous chromosomes fail to separate (or sister chromatids fail to separate in mitosis)
