Genetic Disorders and Syndromes PDF

CYTOGENETICS CSU MLS 2ND YEAR PROF. KEITH TAGUINOD | S.Y 2024-2025 UNIT 10 : GENETIC DISORDERS AND SYNDROMES two-year-old Homo erectus child. Homo erectus was a...

CYTOGENETICS CSU MLS 2ND YEAR PROF. KEITH TAGUINOD | S.Y 2024-2025 UNIT 10 : GENETIC DISORDERS AND SYNDROMES two-year-old Homo erectus child. Homo erectus was a precursor of modern man. TOPIC OVERVIEW 10 Genetic Disorders and Syndromes 10.1 Autosomal Disorders Major Types of Genetic Disorders 10.2 Sex-Linked Disorders 10.3 Chromosomal Genetic Disorders Autosomal Sex-Linked 10 GENETIC DISORDERS AND SYNDROMES Chromosome Abnormalities A genetic disorder is an illness caused by one or 10.1 AUTOSOMAL DISORDERS more abnormalities in the genome, especially a condition that is present from birth (congenital). Autosomal Genetic Disorders are caused by Most genetic disorders are quite rare and affect alleles on autosomes (Chromosomes other than the one person in every several thousands or millions. sex chromosomes) Genetic disorders may or may not be heritable, i.e., Most are recessive (need 2 recessive alleles to have passed down from the parents' genes. the disorder) In non-heritable genetic disorders, defects may be ○ People with 1 recessive allele are carriers — caused by new mutations or changes to the DNA. they DO NOT have the disorder but are able to The defect will only be heritable if genetic disorder pass the allele on to their children occurs in the germ line. ○ Ex: CF/cystic fibrosis, sickle cell anemia ○ Germline : in biology and genetics, the Can also be dominant ( need only 1 allele to have germline of a mature or developing individual is the disorder) the sequence of germ cells that have genetic ○ Ex: huntington’s disease material that may be passed to a child. Cystic Fibrosis Facts A genetic disorder that affects the respiratory Earliest evidence of hereditary genetic and digestive systems disorder discovered: People with Cystic Fibrosis inherit a defective gene on chromosome 7 called CFTR (cystic fibrosis transmembrane conductance regulator) ○ The protein produced by this gene normally helps salt (NaCl) move in and out of cells The fossil is dated as 1.5 million years old and is from a TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 10 : GENETIC DISORDERS AND SYNDROMES Patients with this disease have mutation in a gene on chromosome 11 that codes for the beta subunit of the hemoglobin protein ○ As a result, hemoglobin molecules don not form properly, causing red blood cells to be rigid and have a concave shape (like a sickle) Galactosemia A rare disorder which affects the body’s ability to break down a food sugar called galactose The body breaks down lactose into galactose and glucose and uses these sugars for energy Most people with galactosemia are missing an enzyme called GALT (Galactose-1-phosphate uridyltransferase) that helps further break down galactose Defects in galactose metabolism cause toxic chemicals to build up in cells of the body Fibrodyplasia Ossificans Progressiva (FOP) Also known as Stone Man Syndrome Sickle Cell Disease Extremely rare genetic disease/ World’s rarest A disorder that affects the red blood cells, disease which causes soft tissue to turn into which use a protein called hemoglobin to bone transport oxygen from the lungs to the rest of the body Normally, RBCs are round and flexible so they can travel freely through the narrow blood vessels. Hemoglobin molecule has 2 parts: ○ Alpha ○ Beta TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 10 : GENETIC DISORDERS AND SYNDROMES 10.2 SEX-LINKED DISORDERS Are almost always caused by mutant alleles on the X chromosome ○ Hemophilia Severe Combined Immunodeficiency (SCID) ○ Red-green colorblindness Is a group of very rare and potentially Women can be carriers, but men cannot fatal-inherited disorders related to the immune system People with SCID have a defect in their immune system that leaves them vulnerable to potentially deadly infections Most common form is caused by a mutation in the SCIDX1 gene located on the X chromosome ○ This gene encodes a protein that is used to construct a receptor called Hemophilia IL2RG (interleukin-2 receptor) Caused by an abnormal gene for a blood ○ This receptors reside in the plasma clotting factor membrane of immune cells Blood does not clot normally, so even tiny cut ○ Their job is to allow 2 types of can result in excessive bleeding immune T-cells and B-cells to communicate Red-Green Colorblindness ○ When the gene is mutated, the receptors cannot form and are absent Caused by an abnormal gene for from immune cells photoreceptors in the retina ○ As a result, the immune cells cannot The genes for both red and green communicate with one another about photoreceptors are located on the X invaders in the environment. Not chromosome enough T and B cells are produced to Colorblindness can result from recessive fight o the infection, and the body is alleles for either one or both of these genes left defenseless. ○ Some of the infections include: pneumonia (lung infection) meningitis (brain infection) TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 10 : GENETIC DISORDERS AND SYNDROMES sepsis (blood infection) Babies with cri-du-chat are usually small at birth, and may have respiratory problems. 10.3 CHROMOSOMAL GENETIC DISORDERS Often, the larynx doesn't develop correctly, In these disorders, entire chromosomes, or which causes the signature cat-like cry. large segments of them, are missing, duplicated, or otherwise altered. Can be organized into two basic groups: ○ Numerical Abnormalities: Monosomy- when an individual is missing either a chromosome from a pair Trisomy- has more than two chromosomes of a pair ○ Structural Abnormalities: Down Syndrome - when the chromosome’s structure is altered also known as Trisomy 21 Some Examples: Is a developmental disorder caused by an ○ Cri-Du-Chat Syndrome, extra copy of chromosome 21 ○ Having an extra copy of this ○ Down Syndrome, chromosome means that individuals ○ 47 XXY Klinefelter Syndrome have three copies of each of its genes ○ Turner Syndrome (Monosomy) instead of two, making it difficult for ○ William Syndrome cells to properly control how much protein is made. Cri-Du-Chat Syndrome ○ Producing too much or too little The name of this syndrome is French for "cry protein can have serious of the cat" referring to the distinctive cry of consequences. children with this disorder. People with Down syndrome have very The cry is caused by abnormal larynx distinct facial features: development, one of the many symptoms ○ a flat face associated with this disorder. ○ a small broad nose Caused by a deletion (the length of which may ○ abnormally shaped ears vary) on the short arm of chromosome 5. ○ a large tongue Multiple genes are missing as a result of this ○ upward slanting eyes with small folds deletion, and each may contribute to the of skin in the corners symptoms of the disorder. TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A  UNIT 10 : GENETIC DISORDERS AND SYNDROMES People with Down syndrome have an for male sexual development) are lower than increased risk of developing a number of average. medical problems: As adults, nearly all XXY males are unable to ○ respiratory infections make sperm and so cannot have biological ○ gastrointestinal tract obstruction children. ○ leukemia Many men discover their condition only after ○ heart defects they seek medical help for infertility. ○ hearing loss Changes that appear at puberty can include: ○ hypothyroidism ○ low growth of facial and body hair ○ various eye abnormalities ○ low growth of development of breast No cure exists for Down syndrome. tissues But physical therapy and/or speech therapy ○ small testes can help people with the disorder develop more normally. Turner Syndrome Caused by a missing or incomplete X Klinefelter Syndrome chromosome. 47, XXY (or XXY) People who have Turner syndrome develop as a genetic condition caused when someone has females. two X chromosomes and one Y chromosome. The genes affected are involved in growth and Because people with an XXY chromosome sexual development, which is why girls with arrangement have a Y chromosome, they are the disorder are shorter than normal and have considered genetic males. abnormal sexual characteristics. Most XXY individuals develop as males, often 45,X or 45,X/0 not knowing they have an extra chromosome. XXY is usually caused by what is called Williams Syndrome nondisjunction. A rare genetic disorder that affects a child's: ○ Nondisjunction happens when a pair ○ growth of sex chromosomes fails to separate ○ physical appearance during egg (or sperm) formation ○ cognitive development (meiosis). People who have Williams syndrome are The XXY chromosome arrangement affects missing genetic material from chromosome 7, primarily sexual development. including the gene elastin. Typically, testes don't fully develop, and the levels of the hormone testosterone (important TRANSCRIBED BY: STEPHANIE P. TORRES (gf ni wonwoo) | MLS 2A