Cholesterol Proteins
This protein captures LDL particles from the bloodstream and brings them into the cell.
LDL receptor
This gene that codes for the LDL receptor is located on chromosome 19.
LDLR
A disease caused by a mutation in a single gene that strongly affects a biological process is known as this type of genetic disease.
Monogenic disease
This type of cell division reduces chromosome number by half to produce gametes.
Meiosis
Scientists use this type of study to compare the genomes of many individuals to identify genetic variants linked to disease.
Genome-Wide Association Study (GWAS)
This protein is part of the LDL particle and helps it bind to the LDL receptor.
ApoB
Different versions of the same gene caused by mutations are called this.
Alleles
Some traits do not follow simple Mendelian inheritance because they are influenced by many genes that each contribute small effects. What type of trait is this called?
Polygenic trait
The random orientation of homologous chromosome pairs during metaphase I leads to this source of genetic variation.
Independent assortment
The complete set of DNA, including all genes and noncoding sequences, in an organism is called its ______.
Genome
This protein attaches to LDL receptors and prevents them from being recycled back to the cell membrane.
PCSK9
The pair of alleles someone has for a gene is called their ______.
Genotype
About what percent of people with high cholesterol and a family history have mutations in LDLR, APOB, or PCSK9?
About 40–60%
The fusion of genetically unique gametes to form a zygote is called this.
Fertilization
When a genetic variant appears linked to a disease but may not actually cause it, scientists describe this as this type of relationship.
Correlation
Mutations in LDLR, APOB, or PCSK9 all lead to this result in the bloodstream.
High LDL cholesterol in the blood
Scientists have discovered nearly this many mutations in the LDLR gene.
About 2,000 mutations
Scientists calculate this score by adding the effects of many gene variants to estimate someone's genetic risk for a disease.
Polygenic Risk Score
Human somatic cells have 46 chromosomes. Explain why meiosis must produce gametes with 23 chromosomes for normal fertilization.
Gametes must contain 23 chromosomes so that when sperm and egg combine during fertilization, the zygote receives 46 chromosomes (23 from each parent). This maintains the correct chromosome number in humans.
Researchers found genes like ANGPTL3, MYLIP, CYP7A1, and OSBPL7 that affect cholesterol in small ways. What does this suggest about the genetics of heart disease?
It suggests heart disease is often polygenic, meaning many genes contribute small effects to cholesterol levels and disease risk.
Explain why increased PCSK9 activity can lead to higher LDL cholesterol levels.
PCSK9 causes LDL receptors to be broken down faster, reducing receptors that remove LDL
Explain why mutations in APOB can increase cholesterol levels even if LDL receptors are normal.
ApoB mutations prevent LDL particles from binding properly to LDL receptors
A person has small cholesterol-raising variants in several genes. Why could this still lead to high LDL levels?
Small effects from many genes can add together, increasing LDL cholesterol levels.
Humans have 23 chromosome pairs. Explain how independent assortment and random fertilization together create billions of possible genetic combinations in offspring.
Independent assortment creates about 8.4 million possible gametes (2²³) per parent. Random fertilization combines these gametes, producing over 70 trillion genetic combinations, making siblings genetically unique.
Explain why identifying genes with small effects through GWAS can still be important for predicting disease risk.
Even small genetic effects can add together across many genes, helping scientists estimate risk using tools like polygenic risk scores.