L10 Flashcards
What are the effects of translocation on chromosome behaviour
can affect gene dosage, the fertility of heterozygotes and the expression of genes
what is the difference between euploids and aneuploids
euploids: contain multiple copies of whole chromosome sets whislt…
aneuploids: contain multiple copies of one or more individual chromosomes
What are the two groups which euploids can be divided into
autopolyploids and allopolyploids
what are autopolyploids
have multiple copies of the same genome and consequently have different, though highly characteristic patterns of meiotic chromosome pairing
what are alloployploids
contain multiple copies of different genomes which are derived from different species; important in selective breeding in many crop plants
true or false, aneuploids are much less common than euploids
true
what is translocation
it involves the movement of genetic material between non homologous chromosomes of within the same chromosome (less common)
what are the two types of translocation
reciprocal and non reciprocal
true or false, translocation changes chomosome structure
true
true or false, translocation can physically link genes that were previously located on different chromosomes
true
What is Neurofibromatosis
is a genetic disease characterised by numerous fibrous tumours of the skin and nervous system; this was mapped by using translocation break points
true or false, translocations can result in abnormal meiotic configurations
true
why does a cross like configuration form between homologous chromosomes in prophase 1
this is because the chromosomes have parts of the to other homolog with it due to reciprocal translocation
why do chimps, gorillas and orangutans have 48 chromosomes whereas humans have 46 chromosomes
due to a translocation loss of a chromosome in humans
what is a numerical mutation
changes in chromosome number that can have a major impact on on the development and have an impact on the evolution of most organisms
true or false, human chromosome 2 contains a Robertsonian translocation that is not present in chimps, apes and orangutans
true
true or false, is a diploid a type of euploid
true, AA BB CC two of each
what are the two classifications of chromosome number
euploidy and aneuploidy
What is polyploidy
polyploidy are organisms that have more than two sets of chromosomes
true or false, polyploidy is very common in plants but rarer in animals
true
true or false, polyploidy is one of the major mechanisms by which new plant species have evolved
true
true or false, in polyploidy there is often a correlation between the number of copies of the chromosome set and the size of the organism
true
is there a correlation in plants, the cell volume is correlated with nuclear volume and the genome size
true
what are the two groups that polyploidy is divided into
allopolyploids and autopolyploids
what is an autopolyploid
has multiple chromosome sets from one species
what is an allopolyploid
have multiple sets from two or more species
true or false, autopolyploids 3n can arise naturally when meiosis fails and diploid gametes are produced
true
how are triploids 3n produces
by crossing over 4n and 2n
true or false, triploids are characteristically sterile because of unpaired chromosomes at meiosis
true
true or false, polyploids can be made by treating plants with colchicine, a drug that inhibits spindle formation
true
what is an allopolyploid
a plant that is a hybrid between two or more species; arise as a result of hybridization between two closely related species with subsequent chromosome doubling
what is aneuploidy
the change in the number of individual chromosomes
how can aneuploidy arise (3)
- a chromosome may be lost in the course of mitosis or meiosis if for example its centromere is deleted
- small chromosomes generated by translocations may be lost in mitosis or meiosis
- aneuploid gametes may arise through non disjunction, the failure of homologous chromsomes or sister chromatids separating in mitosis or meiosis
what is monosomic aneuploid
2n-1; A BB CC(eg)
trisomic
2n +1
nullisomy
2n-2
tetrasomy
2n+2
true or false, non disjunction is the most common cause of aneuploidy in both meiosis and mitosis
true
true or false, meiotic non disjunction is more common
true; at meiosis 1 is the most common
true or false, crossing over is necessary for normal chromosome pairing and with out it non disjunction at meiosis 1 increases
true
compare non disjunction in mitosis and meiosis
- Mitotic non disjunction can occur during development and result in sections of the body being aneuploid whilst in meiotic non disjunction the gametes are affected leading to the whole organism being aneuploid
in meiosis where can non disjunction occur
chromosomes may fail to separate at either the first or second meiotic division
true or false, aneuploidy usually alters the phenotype dramatically
true
true or false, aneuploidy alters the dosage of some but not all genes (all genes located on that chromosome will be affected), as a result aneuploidy disrupts the relative concentrations of gene products and thereby interferes with normal development
true
why is it less lethal when aneuploid occurs in sex chromosomes
for example the extra X chromosome is inactivated and the Y chromosome carries a few genes
what is the most common human autosomal aneuploidy
Down Syndrome; trisomy 21
true or false, people with down syndrome carry 3 copies of chromosome 21 ; primary down syndrome
true
true or false, about 75% of the non disjunction even are maternal in origin and most arising in meiosis 1
true
what is familial down syndrome
due to the translocation of genes between chromosome 21 and 14; approx. 4% of people
