Genetics Flashcards
dihybrid
a cross involving two different genes
linkage map
a map based on recombination frequencies
nondisjunction
when chromosomes do not separate correctly during cell division
duplication
mutation where extra chromosomal fragments attach to one of the sister chromatids of homologous chromosomes
pedigree
family tree that follows traits through generations
multiple alleles
genes that have more than 2 allelic forms
phenotype
how an organism looks
test cross
done to find out the genotype of an organism that shows the dominant phenotype (cross dominant organism with homozygous recessive)
particulate hypothesis
all alleles keep their own individual identities; when parents pass on traits, they keep their identities and do not blend together
SRY gene
gene on the Y chromosome that tells a zygote to develop into a male instead of a female
translocation
a piece of one chromosome breaks off and attaches to a non-homologous chromosome
fetoscopy
process to examine a fetus that uses a thin tube with a viewing scope inserted into the uterus
amniocentesis
process when a needle is inserted into the amniotic sac to remove some of the amniotic fluid; cells of the fetus are cultured and used to make a karyotype to look for genetic disorders
pleitropy
genes that affect more than one phenotypic character
cytological map
map of a chromosome that uses chromosomal banding patterns to determine the location of genes on the chromosome
chromosomal theory of inheritance
genes have a specific locus on the chromosomes and that chromosomes undergo segregation and independent assortment during meiosis
punnett square
tool used to help predict the genotypes and phenotypes of future generations
homozygous
another term for true-breeding; having two of the same alleles
blending hypothesis
genetic information from both parents mixes (does not retain its individual characteristics), and that over lots of generations we will get a uniform population
law of independent assortment
each pair of alleles segregates into gametes independently
x-inactivation
when, in females, one of the X chromosomes becomes almost totally inactive and turns into a barr body
monosomy
having one copy of a chromosome
genomic imprinting
when the phenotype of the gene depends on whether it came from the mom or dad
chorionic villis sampling
tube is put in through the cervix and some of the fetal tissue is suctioned out from the placenta; gives immediate results when looking for genetic disorders
dominant
in a heterozygote, this is the allele that is fully expressed in the phenotype
complete dominance
type of inheritance where if an organism has one copy of the dominant allele, the phenotype of that organism will be totally dominant
barr body
when x-inactivation occurs, the x chromosome that becomes inactive turns into this
monohybrid
cross with only one trait
heterozygous
when an organism has a copy of each allele
polygenic inheritance
when two or more genes affect one phenotype; usually represented by continuum of phenotypes; characters have an additive effect
polyploidy
more than 2 complete chromosome sets
aneuploidy
abnormal chromosome number
ultrasound
non-evasive and looks for direct and major anatomical abnormalities
mitochondrial dna
dna inherited only from the mother
sex-linked
genes that are carried on the x or y chromosome
hybridize
another term for cross pollinating
law of segregation
encompasses 4 general ideas and says that 2 alleles for a character are packaged into separate gametes
trisomy
having 3 copies of a chromosome instead of the normal 2
deletion
when a piece of a chromosome is missing
inversion
when a piece of a chromosome breaks off and then reattaches in the wrong orientation
codominance
when 2 different alleles both have an impact on the phenotype
recessive
the allele that gets hidden in a heterozygote; the parts that’s not expressed
genotype
an organism’s genes
crossing over
makes new combinations of linked genes during meiosis
epistasis
a gene at one locus affects the expression of a gene at a second locus
incomplete dominance
heterozygote produces a mix between both alleles
true breeding
another term for homozygous
down syndrome
aneuploid
most sexually undeveloped or sterile
due to nondisjunction during gamete production
klinefelters
aneuploid - XXY
extra X in a male; trisomy 23
male sex organs but sterile
feminine characteristics
normal intelligence
turners
aneuoploid - X0
one X; monosomy x (mono. 23)
phenotypically male; sterile
most have normal intelligence
cri du chat
deletion
deletion in part of chromosome 5
mentally retarded, small head, unusual facial features
baby’s cry sounds like a distressed cat
infant or early childhood death
chronoic myelogenous lukemia
translocation (between 22 and 9)
type of cancer of the blood
prader-willi syndrome
imprinting
develops if receive allele from dad (del. in chromo 15)
mental retardation, obesity, short stature, small hands and feet
fragile x syndrome
imprinting
abnormal x chromosome - tip hangs by thin thread of dna
more common when inherited from mother
mental retardation
colorblindness
x-linked
red-greed vision
hemophilia
sex-linked
absence of one or more clotting factors
blood clots form slowly –> prolonged bleeding
duchenne muscular dystrophy
sex-linked
absence of x-linked gene for key muscle protein called dystrophin
progressive weakening of muscles, loss of coordination
rarely live past early 20s
huntington’s disease
autosomal dominant
deterioration of nervous system
doesn’t show until mid to late 30s
leads to death
tay-sachs
autosomal recessive
brain cells have defective enzyme - doesn’t metabolize lipids –> buildup causes brain not to function properly
death within several months
PKU
autosomal recessive
cannot properly break down AA phenylalanine - accumulate toxic levels, cause mental retardation
strict diet, usually develop normally
cystic fibrosis
autsomoal recessive
most common lethal genetic disease in US
high level of Cl- leads to buildup of mucus - leads to bacterial infections
immune system remains add to mucus
sickle cell
autosomal recessive (demonstrates pleiotropy)
most common inherited disorders in African Americans
cause of sub of one amino acid in hemoglobin protein of red blood cells
oxygen low –> sickle cell hemoglobin molecules crystallize into rods
being carrier is beneficial - resistant to malaria
achondroplasia
autosomal dominant
dwarfism
homozygous dominant = lethal
heterozygous = dwarf
homozygous recessive = normal height
angelman syndrome
imprinting
develop if recessive allele from mom (del. in chromo 15)
spontaneous laughter, jerky movements, other motor/mental symptoms
