Chapter 3 Genetics

Gametes

Sex cells (egg and sperm cells)

Haploid

Only one copy of each chromosome (1 sex chromosome, 22 autonomies)

Gonads

Paired structures where sperm or eggs are manufactured (testes, ovaries)

Meiosis

Type of cell division that halves the chromosome number (Gamete formation)

Homologous pair

One maternal chromosome, one paternal chromosome (SAME genes in the SAME order but may carry DIFFERENT alleles)

Without meiosis, gametes would remain ___ and a fertilized ovum would be ___

Diploid, polyploid (have twice the number of chromosomes)

Since meiosis has ___ cell divisions, ___ haploid cells with 23 chromosomes

2, 4

Meiosis 1 (Reduction Divison)

Homologous chromosome pairs separate (reduces chromosome number from 46 to 23)

Meiosis II (Equational Division)

Sister chromatids separate (produces four non identical haploid daughter cells)

Synapses

Pairing of two homologous chromosomes lineup next to each other (4 chromatids: 2 from each parent)

Crossing Over

Two chromosomes of a homologous pair exchange genetic information with each other (occurs after interphase where DNA is replicated)

Independent assortment

Inheritance of a gene on one chromosome does NOT influence the inheritance of a gene on a different chromosome

Spermatogeneis

Sperm cell formation and differentiation that occurs in the seminiferous tubules of the testes (end product of four same sized sperm cells)

Oogeneis

Oocyte (egg cell) formation that occurs in the ovaries (end product of 3 polar bodies and cell cycle completes ONLY when fertilization occurs)

Maternal Age Effect

The older a gamete is the more likely it is to have a NEW mutation (NOT inherited): occurs when offspring has an extra or missing chromosome

Paternal Age Effect

Condition that arises from stem cell in testis that divide every 16 days once male reaches puberty (these mutations cause skeletal growth abnormalities) DOMINANT single gene mutation

Mutations in the ______ arise more frequently as a man ages

Fibroblast growth factor receptor (FGFR)

Zygote

Unicellular organism from the fertilized ovum stage until formation of the embryo (-2 weeks)

Embryo

Multicellular organism that develops from a zygote (2-8weeks)

Fetus

Start of 9 weeks-birth

Cleavage

Frequent mitosis divisions that produce blastomeres

Morula hollows out and fills with fluid to form a ___

Blastocyst

Blastomeres aggregate to form a

Morula

Ectoderm

OUTERMOST layer closet to the amniotic cavity (skin, nervous tissue)

Mesoderm

MIDDLE layer (muscle, connective tissue, reproductive organs, kidneys)

Endoderm

INNERMOST layer closest to the blastocyst cavity (liver, pancreas)

Dizygotic (fraternal twins)

Two sperm fertilize two oocytes (same genetic relationship as two siblings)

Monozygotic (identical twins)

Arise from a SINGLE fertilized ovum GENETICALLY identical

By the end of week ___, all the organs that will be present in a newborn have begun to develop

8

______ are last to mature

Digestive and respiratory systems

Birth defects caused by teratogens are ____, but whether a teratogen will cause a defect ___

Not genetic, may be genetic

Progeroid disorders

Group of rate single gene disorders which mimic physiological aging, making individuals appear to be older than they are (inability of cells to adequately repair DNA)

Hutchinson-Guilford progeria syndrome

Cells die after only 10-30 divisions (versus 50 in a healthy cell) caused by a single DNA base change in the gene that codes lamin A: life span 13 years

Grastula

An embryo at the stage when it is a hollow cup-shaped structure having THREE germ layers

The cells in each germ layer begin to form specific organs

Blastomeres

Cells that result from cleavage of a fertilized ovum (frequent mitotic divisions)

Morula

Early stage embryo consisting of 16+ blastomeres in a solid ball