genetics Flashcards by Nayana T

incomplete dominance

the heterozygote has an intermediate phenotype

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co dominance

the heterozygote displays the result of both alleles

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epistasis

one gene masks the expression of another

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sex linkage

if a gene is on one of the sex chromosomes, the phenotype and a genotype ratios vary for males and females

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dominant allele

if you have it, you have a parent who did

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recessive alleles

can skip generations

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sex linked

mostly seen in males, can skip generations

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amniocentisis

14-20 weeks
small sample of amniotic fluid taken with a needle
fetal cells in the fluid are cultured
karyotype prepared
pro: can diagnose non disjunction disorders
con: small risk of miscarriage

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chorionic villus sampling (cvs)

8-10 weeks
small sample of cells from placenta is extracted with a suction tube inserted through cervix –> can be cultured and karyotyped
pro: can diagnose non-disjunction disorders earlier than amniocentisis
con: small risk of miscarriage

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trisomy 18

Edwards Syndrome
die within 1 year
organ abnormalities
small head/jaw

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XXY

Klinefelter Syndrome
2n + 1
male
breast development and wide hips
learning disabilities
poor beard growth
infertile

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monosomy

XO
2n-1
Turner Syndrome
female
no puberty
short stature
infertile

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genotype

GG or gg or Gg

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phenotype

purple or white flower

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centromere

links a pair of sister chromatids (centre part of chromosome)

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centriole

organelle near nucleus –> involved in development of spindle fibers

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centrosome

facilitates organization of spindle fibers

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chromosome

DNA molecule, made up of proteins and DNA organized into genes

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chromatid

one of two identical halves of a chromosome that has been replicated

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chromatin

mix of DNA + histones that form chromosomes –> packages long DNA to compact/dense structures

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histone

protein found in chromatin, bind to DNA

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nucleosome

segment of DNA wound around 8 histones

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prophase

1st phase of mitosis where cells thicken and condense

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metaphase

spindle captures all chromosomes and lines them up on opposite ends

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anaphase

sister chromatids separate and pull towards opposite ends

telophase

cell is nearly done dividing and starts to re-establish normal structure

mitosis

4 stages of cell divisions

meiosis

mitosis for sex cells

sister chromatids

identical copies formed by DNA replication that are joined with centromere

crossing over

allows new combos of genes (alleles) even if they're on same chromosomes

synapsis

pairing of homologous chromosomes

chiasma

site of crossing over

tetrad

each pair of homologous chromosomes

bivalent

a pair of homologous chrome

ploidy

number of sets of chromosomes

haploid

having a single set of unpaired chromosomes

diploid

2 sets of chromosomes --> been paired (2 haploids = diploid)

zygote

fertilized egg

somatic cell

every cell in the body that isn't a sex cell

gamete

sex cells

cytokinesis

dividing of the cytoplasm

nucleotide

monomer of nucleic acids made up of sugar, phospate, and a nitrogenous base

nucleoside

nitrogenous base and sugar

purine

adenine, guanine

pyrimidine

thymine, cytosine, uracil

ribose

sugar found in RNA

deoxyribose

sugar found in DNA

phosphate group

chemical group consisting of a phosphorous atom bonded to 4 oxygen atoms

nitrogenous base

carbon ring structures that contains 1 or more atoms of nitrogen

adenine

pairs w/ thymine in DNA

cytosine

pairs w/ guanine in DNA

guanine

pairs w/ cytosine in DNA

thymine

pairs w/ adenine in DNA

uracil

pairs w/ adenine in RNA

hydrogen bond

weak attraction between a hydrogen atom and another atom

double helix

DNA shape

non disjunction

error in meiosis in which homologs fail to separate

aneuploidy

abnormal number of chromosomes

DNA

deoxyribose nucleic acid

RNA

ribose nucleic acid

homologs/homologous chromosomes

pair of chromosomes with the same gene information

deletion

removes a chromosomal segment

translocation

fragment of homologous chromosome attachs to nonhomologous chromosomes

inversion

segment of a chromosome is reversed end to end

duplication

part of the chromosome is repeated

mutation

random fertilization phenylketonuria any change in DNA sequence that can result from replication errors during cell division or DNA - damaging agents in environment

spindle fibers

protein structures which move the chromosomes during cell division

independent assortment

random distribution of pair of genes on different chromosomes to the gametes

polymer

long chain of repeating subunits (nucleic acids, proteins, polysaccharides)

monomer

subunits (monosaccharides, nucleotides, amino acids)

prophase 1

chromosomes condense, nuclear membrane breaks down, crossing over occurs

metophase 1

chromosomes line up in 2 rows w/ homologs

anaphase 1

homologs separate

telophase 1

chromosomes reach end of cells, nuclear membrane form

prophase 11

new spindle forms around chromosomes

metophase 11

centromes of paired chromosomes align

anaphase 11

sister chromatids separate

telophase 11

spindle fiber disappears, nuclear membrane forms around each set of chromosomes (cytokinesis)