NUCLEIC ACID N CHROMOSOMES Flashcards
is RNA or DNA more stable?
- DNA is more stable as it is less reactive due to C-H bond at 2’ carbon
- RNA is less stable as it is more reactive due to O-H bond at 2’ carbon
where is DNA found in eukaryotes and prokaryotes?
Eukaryotes : found in the nucleus
Prokaryote : circular, double-stranded DNA floats freely in the cytoplasm (nucleoid)
what are purines and pyrimidines?
Purines : Adenine and Guanine (two rings)
Pyrimidine : Cytosine and Thymine (one ring)
How are DNA nucleotides joined together?
Dehydration reaction which produces water and phosphodiester bond between two nucleotides
What can genetic material do?
- must carry information ; genetic code
- must be able to replicate ; DNA replication
- must allow information change ; mutation
- govern the expression of the phenotype ; gene function
How is DNA packaged?
DNA is wrapped tightly around histones and coiled tightly to form chromosomes
What are histones?
a family of basic proteins that associate with DNA in the nucleus and help condense it into chromosome
What are nucleosomes?
section of DNA wrapped around histone
What are chromatin?
DNA and Histone proteins are collectively called chromatin
Whats is DNA?
molecule that encodes the gentic information
What are chromosomes made of?
- chromosomes are made up of many genes
- long strings of DNA wrapped tightly around histones which contributes to the threadlike structure
What are autosomes?
chromosome 1-22 in humans which looks the same in both female and male
What are sex chromosomes?
23rd pair of chromosomes which determines the gender
what do female and male chromosomes look like?
female : XX (homogametic)
male : Xy (heterogametic)
What is karyotyping?
a system to identify chromosomes by their size, shape and banding patterns produced by specific stains
- chromosomes are analysed by organising them into
karyotype
What is Giemsa Staining?
staining chromosomes, specific for phosphate groups of DNA and attaches itself to regions of DNA where there are high amounts of A-T bonding
what are alleles?
variant forms of a given gene
- each organism has a pair of allele for each trait ; 1 mother, 1 father
What is homozygote?
HOMOZYGOUS : two identical alleles for a gene
What is heterozygote?
HETEROZYGOUS : two different alleles for the same gene
What does dominant allele do?
mask the expression of recessive allele
What is genotype?
gentetic compostion of individual
What is AA?
homozygous dominant genotype
What is aa?
homozygous recessive genotype
What is Aa?
heterozygous genotype
What is phenotype?
characteristics that are the result of gene expression
What is punnet square?
used to predict traits of an off-spring
What is incomplete dominance?
appearance in a heterozygote of a trait that is an intermediate between either of the trait’s homozygous phenotypes
What is co-dominance?
alleles of a gene pair are fully expressed resulting in an off-spring with a phenotype that is neither dominant nor recessive
What are multiple alleles?
a series of 3 or more alternative alleles forms of a gene
e.g ABO blood type is controlled by a single gene (ABO gene)
What is gene mutation?
permanent alteration in the DNA sequence that makes up a gene such that the sequence differs from what is found in most people
e.g sickle cell gene disorder
What is cancer?
multifactorial and progressive genetic disorder
what are chromsomal disorders?
Down syndrome (Trisomy 21)
- chromosome 21 does not separate correctly
- develop slower, heart & stomach illness and vary greatly in IQ
