6 from chromosomes to genomes Flashcards
structure of deoxyribonucleic acid (DNA)
double helix: two polynucleotide chains that coil around each other
- DNA codes genetic instructions for the development, function, growth and reproduction of organisms
Define and know a nucleotide
a sub-unit of DNA consisting of a phosphate group,
a nitrogenous base and a sugar
phosphate group - circle
pentose sugar - pentagon
nitrogenous base - rectangle
Complementary base pairs of nitrogenous bases
Adenine - Thymine
Guanine - Cytosine
Define and describe the function of a gene
a section of a chromosome that codes for a protein through the order of the nucleotide base sequence
explain alleles - hetero and homo
alleles: the different forms of a gene
heterozygous: two different alleles of a gene
homozygous: two identical alleles of a gene
Differentiate genes and alleles
alleles are forms of genes whereas a gene is a section of a chromosome that codes for a protein
define genome
the sum total of an organism’s DNA
explain the nature of homologous choromosomes with reference to gene loci
homologous: matching pairs of chromosomes that have the same genes at the same positions (loci)
define autosome
any pair of homologous chromosomes that are identical in appearance in both males and females
define and know the diff sex chromosomes
a pair of chromosomes that differ in males and females of a species; allosomes
XX - female
XY - male
Define haploid and diploid
diploid (2n): two copies of each chromosome in each set
- only somatic cells (46)
haploid (n): one copy of each chromosome in each set
- only gametes (23)
Describe the purpose of a karyotype
karyotype: an image of chromosomes from a cell arranged in an organised manner
- a visual representation that can be used to identify chromosome abnormalities
explain how karyotype is produced
- cytogeneticists capture an image of chromosome sets from a camera attached to a microscope
- image transfers to computer software that analyses and generates a karyotype
know what characteristics used to create karyotype
- size
- position of the centromere
- banding patterns
Detect chromosomal abnormalities on karyotype
aneuploidy: the presence of an abnormal number of chromosomes
Outline how chromosomal abnormalities may occur
- changes in the total no. of chromosomes
- changes involving part one of chromosome
- changed arrangements of chromosomes
Define and know the difference bw monosomy and trisomy
trisomy: a cell has three copies of a particular chromosome that is normally present as a homologous pair
monosomy: a cell has only one copy of a particular chromosome that is normally present as a homologous pair
define sexual reproduction
define/ know the difference between haploid and diploid
define homologous chromosomes & identify chromosome, chromatid, centromere, sister chromatids
define gametes of males and females, somatic cells
Phases of meiosis and events occurring in each phase, and order events occur.
End result (outcomes) of meiosis/why this is necessary.
Cause of variability – crossing over and independent assortment (define, recognize)
What happens when meiosis goes wrong? Ie. Non-disjunction
what is the waist of a chromosome called
centromere: the position where the chromatids are held together in a chromosome
Draw and name the 4 shapes of chromosome
MSAT
metacentric: centromere in the middle
- p and q arms are equal in length
submetacentric: centromere towards one end
- q arms approx. twice the length of p arms
acrocentric: centromere is very close to one end
- p arms are very short
telocentric: centromere is at the tip
- no p arms
relo bw complexity of an organism and no. of genes and chromosomes it has
