Download
1 / 28
280 likes | 392 Vues
This overview delves into the fundamental concepts of chromosomes and inheritance, distinguishing between autosomes and sex chromosomes. It covers key topics such as alleles, genotypes, phenotypes, and genetic disorders, illustrating how traits are inherited. It explains the differences between autosomal dominant and recessive inheritance patterns, x-linked traits, and the implications of chromosomal abnormalities such as aneuploidy. Real-world examples, including Down syndrome and Huntington’s disorder, highlight the impact of these genetic principles on human health.
E N D
Autosomes vs. sex chromosomes Autosomes = the pairs of chromosomes that are the same in males and females In humans, these are chromosomes # 1 - # 22
sex chromosomes = differ between males and females of a species: differ physically and in the genes they carry In humans, chromosome # 23
female x x xx & male xy y x & sex determination in humans: female gives: male gives:
Alleles alleles are different forms of a given gene ex. gene = tongue rolling tongue roller vs. non-roller
the alleles from mom and dad may be the same, may be different chromosome # 14 tongue rolling gene from mom tongue rolling gene from dad
Each person carries 2 copies of each gene (on their autosomes) Genotype = the gene forms, or alleles someone carries
Genotypes RR- if they carry the same allele on both chromosomes -> HOMOZYGOUS Rr- if they carry different alleles -> HETEROZYGOUS
Phenotype = the physical or physiological expression of those alleles
alleles can have different relationships to each other dominant --- recessive 1. a dominant allele, when found in the heterozygous condition, overrides the recessive allele Rr -> will result in a tongue roller
roller roller non-roller GENOTYPE PHENOTYPE RR = homozygous dominant Rr = heterozygous rr = homozygous recessive
3. multiple alleles with codominance ex. blood type
ex. a person born with 6 fingers Genetic Disorders 1. genetic abnormality- an uncommon version of a trait
2. genetic disorder- an inherited condition that will result in mild to severe health problems. ex. cystic fibrosis
3. syndrome- a set of symptoms that characterize a given disorder
Autosomal dominant inheritance = trait will typically appear in every generation HH or Hh Ex. Huntington’s disorder (nervous system)- typically fatal in 40’s or 50’s Why does gene stay in population? its effects occur post-reproduction
Autosomal recessive inheritance- trait (disorder) shows up less often in the population because the trait can be masked by the dominant allele Ex. galactosemia: gg lactose galactose glucose-1-phosphate glucose X results in a buildup of galactose in blood… damage to eyes, liver, brain
male female x-linked recessive traits- gene is only found on the x chromosome- not the Y! xAxA xAxa xaxa xAy xay 33.3% 50%
Hemophilia in Royal Families in Europe I-1 = King George III III-1 and III-2 = Prince Albert and Queen Victoria IV-5 and IV-6 = Alice of Hesse and Ludwig IV of Hesse V-13 and V-14 = Alix and Nicholas II (Tsar of Russia) VI-16 = Alexei VIII-1 = Prince Charles
Changes in Chromosome Number aneuploidy= the condition of having less than or more than the normal diploid number of chromosomes polyploidy- condition of having 3 or more entire sets of chromosomes (lethal in humans)
Down syndrome (trisomy 21): The result of an extra copy of chromosome 21. Down syndrome affects 1:700 children and alters the child's phenotype either moderately or severely.
cause of aneuploidy = NONDISJUNCTION Failure of paired chromosomes to disjoin (separate) during cell division so that both chromosomes go to one daughter cell and none to the other.
Patau syndrome (trisomy 13): serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months.
