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.
What are genes?
Strands of information found in DNA that provide instruction for making proteins. They
Chromosomes are…
Homologous chromosomes are 99.9% identical, not 100%.
A human cell containing 44 autosomes and two X chromosomes is…
Somatic cell of a female.
A human cell containing 45 autosomes and a normal number of sexual chromosomes is probably…
A somatic cell of a trisomic person.
A fertilized human ovum (zygote) contains how many chromosomes?
46
If a diploid organism has a genome consisting of 22 chromosomes, its gametes will have _____ chromosomes.
11
Define Haploid.
The condition of having one set of chromosomes per nucleus.
Define Diploid
The condition of having 2 set of chromosomes per nucleus.
An X-shaped site in a tetrad marking the location where homologous chromatids previously underwent crossing over
Chiasma
The chromosomal constitution of an individual; generally prepared by photographing the chromosomes and arranging the homologous pairs according to size, centromere position and pattern of bands.
Karyotype
Structure consisting mainly of microtubules that provides the framework for chromosome movement during cell division
Mitotic spindle/spindle apparatus
What can cause nondisjunction?
Misaligned or incomplete synapsis, or a spindle apparatus dysfunction that facilitates chromosome migration, can cause nondisjunction.
What causes chromosomes number disorders?
Duplicating or losing entire chromosomes and changes in the number of complete sets of chromosomes.
What is the except in the organization of the karyotype?
Chromosome 21 is
