RNA and DNA, Genetic Crosses Flashcards
DNA and RNA creator and overview
Watson and Crick
nucleic acids
either dna or rna are present in viruses, never both
chemical composition of chromosomes
DNA and protein
dna structure
double helix
each strand is composed of nucleotides: deoxyribose sugar, phosphate, nitrogeneous base
complementary bases from opposite strands held together by hydrogen bonds
nitrogenous bases
adenine- thymine
cytosine- guanine
dna vs rna
dna - double stranded
rna- single stranded
dna- sugar is deoxyribose
rna - sugar is ribose
dna - bases A,T,C,G
rna - bases A,U,C,G
dna location
nucleous
rna location
cytoplasm , ribosome
genotype
genetic make up eg bb,Bb,BB
phenotype
physical make up eg brown eyes
dominant
where one allele masks the effect of another allele
recessive
where an alleles effect is only expresses when in the homozygous condition
homozygous
two alleles for a trait are the same eg BB
heterozygous
two alleles for a trait are different eg Bb
incomplete dominance
neither allele masks the effect of the other- both alleles are equally expressed in the heterozygous genotype to produce an intermediate phenotype
sex linked
when a gene is located on a sex chromosome
pedigree study
a diagram showing the genetic history of a group of related organisms
linkage
genes for different traits located on the same chromosome
locus
the position of a gene on a chromosome
non nuclear DNA
DNA that is not located in the nucleus ( found in mitochondria)
segregation
separation of alleles
monohybrid crosses
write a key order of cross: parents phenotype parents genotype meiosis and gamete formation fertilisation (punnet square) offspring genotypes offspring phenotypes
incomplete dominance crosses
same steps as monohybrid
sex linked crosses
write a key
write down sex chromosomes for each parent, assign thr correct allele to each chromosome, none to Y
same steps as monohybrid
where does a son get his x and y
y from father
x from mother
if he has a sex linked condition, it must come from the mother as Y doesnt carry many alleles
non-nuclear inheritance
inherited from the mother
can lead to inheritance of muscular disorders such as lack of ATP production
why: during fertilisation, the acrosome of the sperm cell enters the egg to fuse with the nucleus, but the midpiece which contains the mitochondria doesnt enter the egg
in plants: chloroplasts inherited from mother
when both parents are heterozygous for both traits (dihybrid cross)
9:3:3:1
dihybrid crosses
inheritance of two traits
four letters for each parent eg BbHh
same steps as hybrid cross
significance of two allele pairs on different chromosome pairs (not linked)
gives rise to more variation in offspring ( independent assortment)
linkage
genes for different traits are located on the same chromosome
gives rise to less variation as a result of fewer possible gene combinations
Gregor Mendel
father of genetics
studied traits in peas
first experiment mendel
pure bred tall x pure bred small
results: ratio 3:1 tall : small
law of segregation
organisms contain two alleles for every trait
these alleles separate at gamete formation, each of which containing one copy of each allele
second experiment mendel
pure bred tall and purple x pure bred small and white
results: all offspring tall and purple
law of independent assortment
either member of a pair of alleles can pass into a gamete with either member of another pair of alleles
more variation occurs as a result
exceptions to mendels laws
linked genes : are inherited together, give rise to less variation
sex linked genes: where alleles are located on a sex chromosome
purine bases
adenine
guanine
pyramidine bases
cytosine
thymine
DNA replication
production of an identical copy of DNA in a cell
during interphase
1. DNA helix unwinds, hydrogen bonds are broken by enzymes and strands separate
2. complementary base pairs on free nucleotides attach to exposed bases - joined together by DNA polymerase
3. Each DNA molecule winds back into a helix shape
significance of DNA replication
all cells produced as a result of cell division have identical genetic information to each other
DNA profiling
making and examining a pattern of bands from the DNA of one person which can be compared with the DNA profile of another person
describe DNA profiling
- DNA extraction: cells broken down to release DNA
- DNA cut into fragments using restriction enzymes
- Fragments separated by gel electrophoresis based on size (smaller fragments move farther)
DNA (negatively charged) moves toward +ive terminal - Pattern of fragments compared
applications of dna profiling
medicine: look for genetic matches in organ transplants
forensic science: comparing victim and suspect blood samples
relationships: maternity/paternity disputes
genetic screening
testing for the presence of a specific or altered gene
applications:
adult - identifying carriers of a defective gene eg cystic fibrosis, haemochromatosis - deciding whether or not to have a family
embryonic- predictive testing for a genetic disorder
RNA types
mRNA
tRNA
rRNA
messenger rna
located in nucleus
composed of codons complementary to dna strand
three types of codons/ nature of the genetic code:
1. start codon
2. amino acid codon
3. end codon
function: carries info (code) for a specific protein from the nucleus to a ribosome
ribosomal rna
located in the ribosome in the cytoplasm
function : structural component of a ribosome by combining two ribosome subunits together
forms weak bonds with mRNA and attaches tRNA to mRNA
transfer rna
located at the ribosome attached to mRNA
function: transports amino acids to the mRNA and attaches to mRNA
How :
carries anticodons
carries amino acids at the other end and aligns in the correct sequence
transcription
copying a sequence for bases from DNA to mRNA with the aid of RNA polymerase in the nucleus of a cell
outline transcription
DNA unwinds at specific base sequence
RNA nucleotides from cytoplasm match with their complementary DNA bases in the nucleus
RNA polymerase binds the nucleotides together = mRNA
mRNA leaves nucleus
RNA polymerase
anabolic enzyme
structure of a protein
long chain of 20 amino acids
amino acid sequence determines structure and function of the protein
translation
synthesis of proteins by forming chains of amino acids in the ribosome with the help of mRNA , rRNA and tRNA
outline translation
mRNA forms weak bonds with rRNA and ribosome
mRNA contains start codon, amino acid codon, stop codon
tRNA matches its anticodons with complementary codons on mRNA, each tRNA also carries a specific amino acid to the anticodon
tRNA continues to carry amino acids to the mRNA until a stop codon is reached
last step in protein synthesis
proteins fold to carry out its function efficiently, allowing it to reach its 3D shape
