Human Development Lecture 11 – Genetics and inheritance
Human genetic abnormalities;
Multifactorial; erfelijke aanleg samne met andere factoren zorgt voo rziekte
Mutant genes (spontaneous mutations);
o Changes in nucleotide sequence of allele
o Errors in DNA replication
Most errors undergo repair. Not? Then they have potential to change
phenotype.
Chromosomal defects; non-disjunction; chromosomes do not segregate
properly;
o Meiotic nondisjunction; offspring will have abnormal chromosome
number
o Mitotic nondisjunction; tissue will have altered chromosome number.
Euploid; chromosome number = the number of the haploid chromosome set
- Monoploid; one set of chromsomes (n)
- Diploid; two sets of chromosomes (2n)
- Triploid; three sets of chromosomes (3n)
- Tetraploid; four sets of chromosomes (4n)
Aneuploid; chromosome number is NOT the number of the haploid
chromosome set
- Disomic; 2n give rise to tirsomic embryos (zygote)
- Nullisomic; 0n not viable, unless it concers the X/Y chromosome.
Occurs during anaphase meiosis I or II.
Meiosis I; entire bivalent (tweewaardig)
migrates to one pole. Four haploid cells are
abnormal. 2 disomic, 2 nulisomic
Meiosis II; result in 2 abnormal and 2 normal
haploid cells. 2 euploid, 1 disomic, 1
nulsomic.
Only embryonic survivors with a shortage of
one chromosome are those concerning the X-chromosome
Only embryonic survivors with an extra chromosome are those concerting the
X or Y chromosome as well as chromosomes; 13 (Patau, early death), 18
(Edward, early death), 21 (Down, nondisjunction) and 22. Trisomy 9 is
embryonic lethal.
XXY Klinefelter
XYY Jacobs
XXX triple X
X0 Turner
Environmental agents
Most unknown ethiology
Human genetic abnormalities;
Multifactorial; erfelijke aanleg samne met andere factoren zorgt voo rziekte
Mutant genes (spontaneous mutations);
o Changes in nucleotide sequence of allele
o Errors in DNA replication
Most errors undergo repair. Not? Then they have potential to change
phenotype.
Chromosomal defects; non-disjunction; chromosomes do not segregate
properly;
o Meiotic nondisjunction; offspring will have abnormal chromosome
number
o Mitotic nondisjunction; tissue will have altered chromosome number.
Euploid; chromosome number = the number of the haploid chromosome set
- Monoploid; one set of chromsomes (n)
- Diploid; two sets of chromosomes (2n)
- Triploid; three sets of chromosomes (3n)
- Tetraploid; four sets of chromosomes (4n)
Aneuploid; chromosome number is NOT the number of the haploid
chromosome set
- Disomic; 2n give rise to tirsomic embryos (zygote)
- Nullisomic; 0n not viable, unless it concers the X/Y chromosome.
Occurs during anaphase meiosis I or II.
Meiosis I; entire bivalent (tweewaardig)
migrates to one pole. Four haploid cells are
abnormal. 2 disomic, 2 nulisomic
Meiosis II; result in 2 abnormal and 2 normal
haploid cells. 2 euploid, 1 disomic, 1
nulsomic.
Only embryonic survivors with a shortage of
one chromosome are those concerning the X-chromosome
Only embryonic survivors with an extra chromosome are those concerting the
X or Y chromosome as well as chromosomes; 13 (Patau, early death), 18
(Edward, early death), 21 (Down, nondisjunction) and 22. Trisomy 9 is
embryonic lethal.
XXY Klinefelter
XYY Jacobs
XXX triple X
X0 Turner
Environmental agents
Most unknown ethiology
