Human Growth Chapter 2

what is a genotype

an individual’s unique genetic information

what is a phenotype

an individuals directly observable characteristics

what do chromosomes do

they store and transmit genetic information

where are chromosomes found

nucleus

what are chromosomes made out of

protein

how many pairs of chromosomes do humans have

23 pairs

what is DNA

the substance of which genes and chromosomes are made

what shape is DNA

like a twisted ladder

what is a gene

a segment of DNA located along the chromosomes

what is meiosis

the process of cell division that creates gametes

what is a gamete

a sex cell

what are autosomes

22 matching pairs of chromosomes

what pair of chromosomes are sex chromosomes

the 23rd pair

male sex cells are

XY

female sex cells are

XX

what is a zygote

it is formed when sperm and ovum unite

what is an allele

two forms of the same gene, one inherited from each parent

when both alleles are alike it is called

homozygous

when the alleles differ it is called

heterozygous

fraternal twins are called

dizygotic twins

identical twins are called

monozygotic twins

fraternal twins are how many zygotes

2

identical twins are how many zygotes

1 that divides into 2 individuals

recessive alleles have no effect unless

there are two recessive alleles

examples of diseases caused by recessive alleles

sickle cell, PKU, hemophilia, and cystic fibrosis

what is codominance

when both alleles are dominat

codominance example

A blood plus B blood makes AB blood

x-linked inheritance disease examples

color blindness and hemophilia

what is a mutation

a sudden, permanent change in a DNA segment

what are the types of mutations (2)

germline and somatic

germline mutations are

hereditary and present for life

somatic mutations are

acquired, but only in some cells at a certain time

what is down syndrome

results when the 21st chromosome pair fails to separate during meiosis

what does genetic counseling help with

helps couples asses risk of hereditary disorders and choose best course of action

why would someone seek genetic counseling

a couple with difficulty bearing children, known genetic problems exist, or woman is over 35

what is the tool that genetic counselors use

pedigrees

what is amniocentesis

sticking a needle and pulling a sample from the amniotic sac

when is an amniocentesis performed

around 14 weeks

what is a fetoscopy

surgery on the baby in utero

what is the most common prenatal diagnostic method

maternal blood analysis

what is chorionic villus sampling

taking a small part of the placenta and running tests

what percent of US children live in poverty

21%

poverty rates are higher for

children of parents under 25, ethnic minorities, and single mothers

risks of poverty

lifelong poor physical health, poor development, mental illness, aggressive behaviors, impulsivity, and antisocialness

epigenesis studies what

how environment alters gene expression