Chromosomes Flashcards
What are alleles?
Different variations of one gene.
How many chromosomes are in a somatic cell?
46 chromosomes.
Describe a prokaryotic genome.
ONE double-stranded, loop / circle of DNA molecules.
Define Euploid
Individual having correct number of chromosome for their species. (humans: 24)
Define Aneuploid
Individual with an error in chromosome number. (extra / fewer chromosomes)
What is a nondisjunction?
When homologous chromosomes or pairs of sister chromatids fail to separate during mitosis.
What is the outcome of a nondisjunction of homologous chromosomes?
2 gametes will lack 1 chromosome and 2 other will have one more (a copy of one) chromosome.
What is the outcome of a nondisjunction of sister chromatids?
1 gamete will lack a chromosome and 1 other will have one more (one identical). 50% will be normal.
What’s an autosome?
“Body chromosome” all non-sex chromosomes.
Chromosomes X and Y ARE NOT autosomes.
What happens to monosomic human zygote? and why?
It fails to develop at birth, because they lack essential genes.
What does polyploid means?
Abnormal diploid egg + normal haploid sperm = ?
individual with more than the correct number of chromosomal sets (2 for diploid species).
=Triploid zygote
What is the difference between Aneuploid and Polyploid?
Aneuploid: extra/fewer chromosomes.
Polyploid: extra sets.
What are the possible changes in chromosome structure?
Inversion
Translocation
Deletion
Duplication
Explain the process of ‘chromosome compaction’.
DNA is wrapped around protein histones (nucleosome), they coil together to form the CHROMATIN fibber, then (when cell is getting ready to divide) are further condensed and compacted to form CHROMOSOME where genes are accessible.
Pericentric and Paracentri are two types of inversions? What is the difference?
Pericentric: includes centromere.
Paracentric: Ø includes centromere.