Genetics Flashcards
genes
the basic unit of genetic material
defined portion of a chromosome that encodes for a particular trait or substance such as hair color, blood type, etc.
alleles
the different forms a particular gene can occur in
you have 2 copies of each gene
homozygous
2 identical alleles for a particular gene
heterozygous
2 different alleles for a particular gene
dominant
always expressed
indicated by capital letter
recessive
will be masked by a dominant gene
can only be expressed if there is no dominant gene present
indicated by a lowercase letter
codominant
neither masks the other so both are expressed
e.g. blood type
genotype
the makeup of the gene
which 2 alleles are present
phenotype
what actually gets expressed
what you see
punnet squares
the method for predicting the outcome of a cross between 2 parents
make a grid of genotypes
dihybrid cross
cross with 2 different traits
blood types
based on what is on the cells surface
Type A
A antigen on RBCs surface
can’t receive B
can receive A or O
dominant
Type B
B antigen on RBCs surface
can’t receive A
dominant
Type AB
both A and B antigen on RBCs surface
can receive from everyone
codominant
Type O
neither A or B antigen on RBCs surface
can only receive from O, but is the universal donor
recessive
RH blood system
+ or -
+ is dominant
- is recessive
sex determination
XX= female XY= male
hemophelia
most common X-linked disorder
defect in clotting proteins
recessive
color blindness
red/green is most common form
mainly found in males
autosomal recessive disorders
trait is on chromosomes other than the sex chromosomes
must have 2 copies of the gene for it to be expressed
albinism
autosomal recessive disorder
defect in production of melanin
sickle cell anemia
autosomal recessive disorder
defect in the gene making hemoglobin
RBCs have typical sickle shape
PKU
phenylketonuria
autosomal recessive disorder
enzyme defect leads to buildup of phenylalanine in the bloodstream and neurological problems
cystic fibrosis
autosomal recessive disorder
enzyme defect causes the production of abnormal mucus which causes problems in both the respiratory and gastrointestinal tracts
autosomal dominant disorders
only need 1 copy to have the disorder
just 1 parent needs to be the carrier
huntington’s
autosomal dominant disorders
invariably fatal neurological disorder which does not show up until 30 or 40 years of age, after the person has had children and possibly passed the gene on
polydactyly
autosomal dominant disorders
extra fingers and toes
chromosomal & structural disorders
involve physical or structural defects in the chromosomes rather than the genes
often result from nondisjunction, where 1 or more chromosome pairs do not separate during mitosis or meiosis
leads to cells having too many or too few chromosomes due to unequal distribution during cell division
polyploidy
refers to more than the usual amount of a particular chromosome
e.g. XXY (klinefelter syndrome) or XYY
down’s syndrome
polyploidy
also known as trisomy 21 due to the fact that there are 3 copys of that chromosome
associated with structural defects of the face and neurological problems
anuploidy
only 1 copy of the chromosome
e.g. girls with only 1 X chromosome (turner’s syndrome)
DNA structure
nucleic acid composed of 4 bases or nucleotides (A&T, C&G)
base pairing-2 strands of DNA connected by H-bonding between bases in the 2 strands
form double helix
in RNA there is A&U pairing instead of T
DNA replication
strands split
each strand is template for the synthesis of the complementary new strand
DNA polymerase is primarily responsible for this
the genetic code
proteins are strings of AA
each series of 3 bases (codon) codes for 1 AA
start and stop codons mark the beginning and end of the protein
protein synthesis
transcription-1 strand of DNA is read to produce mRNA
translation-mRNA attaches to ribosomes to trigger the production of the protein
codons in mRNA are read by tRNA to place the appropriate AA
mutation
a permanent change in the structure of the DNA which is passed on to the offspring of the effected cell
may or may not have a noticeable effect and the effect may be helpful or harmful
causes of mutations
radiation, chemicals, and viruses
missense mutation
single base is changed
leads to change in codon which leads to a different AA
change in the 1st of the 3 letters will have the greatest impact
nonsense mutation
single base is changed
changes codon to become a STOP codon, which terminates synthesis prematurely
frame shift
addition or removal of an extra base
insertion frame shift
extra base inserted into DNA molecule
throws off the codon it ends up in and all of those downstream from that point (major change)
deletion frame shift
base is deleted from the DNA molecule
throws off the codon it ends up in and those downstream from that point (major change
recombination
transfer of genetic information from 1 organism (donor) to the other (recipient)
transformation
DNA from a dead bacteria which has broken apart is taken up through the cell wall of the recipient bacteria and integrated into its own DNA
conjugation
exchange of a small piece of DNA (plasmid) from 1 bacteria to another
the bacteria are joined together by a sex pilus
transduction
a virus carries genetic information from 1 bacteria to another
transposons
jumping genes
genetic elements that move from 1 place to another within a chromosome
