Unit 4 Flashcards
Interphase
phase that prepares the cell for prophase, contains G1,S,G2
G1 Phase
cell grows, Organelles are replicated, 5-6 hours, checkpoint
S Phase
chromosomes are duplicated, Occurs in the nucleus, 10-12 hours
G2 Phase
more growth, completes preparation for division, 4-6 hours, checkpoint
Prophase I
Homologous chromosomes pair up and form tetrad, crossing over occurs
Metaphase I
Homologs line up along the equator
Anaphase I
Spindle fibers move homologous chromosomes to opposite sides
Telophase I
Cytoplasm divides, 2 daughter cells are formed
Prophase II
Follows meiosis I
Metaphase II
Chromosomes line up along the equator, not in homologous pairs
Anaphase II
Chromatids separate
Telophase II
Nuclear membrane forms, cytoplasm divides, 4 daughter cells
Gamete
sperm, egg cells
Chromatid
one half of a chromosome
Homologous chromosomes (homolog)
A pair of matching chromosomes in an organism, with one being inherited from each parent
Independent assortment
different genes independently separate from one another when reproductive cells develop
Chaismata
point where chromosome touch and crossing over occurs
Spindle fibers
attach to the chromosomes in metaphase, work to split apart chromosomes
Cytokineses
the cytoplasmic division of a cell at the end of mitosis or meiosis
Daughter cells
product of meiosis or mitosis
Haploid
sex cells have half a set
Diploid
body cells have the full set of chromosomes
Meiosis
consists of 2 divisions resulting in 4 daughter cells, each with half the number of chromosomes
Zygote
a diploid cell resulting from the fusion of two haploid gametes
Crossing over
the exchange of genes between homologous chromosomes, resulting in a mixture of parental characteristics in offspring
Gametogenesis
the process in which cells undergo meiosis to form gametes
Homozygous
having two identical alleles of a particular gene (ex. AA, aa)
Heterozygous
having two different alleles of a particular gene (ex. Aa)
Recessive Allele
an allele whose phenotype effect is not observed (ex. a)
Dominant Allele
an allele whose phenotype effect is fully expressed (ex. A)
Allele
any of the alternative versions of a gene that may produce distinguishable phenotypic effects
Character
an observable heritable feature that may vary among individuals
Phenotype
A descriptive of an organisms traits
Genotype
A descriptive of its genetic makeup
F1 Generation
the first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross
F2 Generation
the offspring resulting from interbreeding (self pollination) of the hybrid in F1 generation
Law of segragation
stating that two alleles in a pair separate from each other into different gametes during gamete formation
Law of Independent Formation
stating that each pair of alleles assorts independently of each other pair during gamete formation
Pleiotropic
the ability of a single gene to have multiple effects
Epistatis
a type of gene interaction in which the phenotypic expression of one gene alters that of another independently inherited gene
Polygenic Inheritance
an additive effect of two or more genes on a single phenotypic character
Individuals who lack the disorder are…
either homozygous dominant or heterozygous
Co-dominant
a type of inheritance in which alleles of the same gene are expressed separately to yield different traits in an individual
Incomplete Dominance
a form of gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype
True breeding
an organism that always passes down certain phenotypic traits to its offspring of many generations
Test cross
a cross between an individual displaying a recessive trait and one displaying a dominant trait to determine whether or not the dominant trait is heterozygous
Monohybrid cross
single trait crosses (ex. AA x Aa)
Dihybrid cross
Double trait crosses (ex. AAbb x AaBB)
Chromosomal Theory of Inheritance
states that chromosomes are carriers of genetic information
Karyotype
Shows all chromosomes in an organism, organized by size
Disorders that are recessive are…
masked in females by the other X chromosome
Human Sex Linked Disorders
Colorblindness, Muscular Dystrophy, Hemophilia, Fragile X Syndrome
Muscular Dystrophy
Wasting away of muscles, life expectancy is 20 years
Hemophilia
“bleeders disease”, blood doesn’t clot properly
Fragile X Syndrome
Caused by triplet repeats (duplication mutation) in a gene on the X chromosome, causes mental retardation, tip of the X chromosome seemed to be attached only by a small thread
Non-Disjunction
Changes the chromosome #
Down Syndrome
extra chromosome in #21
Trisomy-18 (Edwards syndrome)
Extra copy of chromosome #18, Failure to grow/gain weight, developmental delays and intellectual disability, physical appearance (malformed ears, small jaw, narrow eyes)
Trisomy-13 (Patau Syndrome)
An extra copy of chromosome #13, 50% of babies die in the first month
Chromosome Mutations
Deletion, Duplication, Inversion, Translocation
Cri Du Chat
Deletion of gene on chromosome #5
