Nov 54 min read

Heritage or Hazard: Genetic Inheritance

Some families pass down priceless jewelry, others pass down meaningful antiques, but the rest? They simply inherit genes. Offspring inherit two copies of each gene from their parents. Single nucleotide polymorphisms (SNPs) are little variations that do not affect how a gene functions, whereas mutations can cause illness. Genes and the environment affect how genes are expressed, and single-gene mutations can result in some genetic disorders. Similarities between people are the product of genetic inheritance, which is the transfer of DNA variants from ancestors to descendants. Our genes are distinct, and all living organisms' traits are determined by genetic inheritance.

A Genetic Gamble
Trust The Process
Sources & Works Cited

A Genetic Gamble

Some of us describe our parents' genetics as "good genes" or "bad genes". But those terms usually refer to appearance; genetics also involve the passing down of inherited diseases or medical conditions that can limit us in some way.

Polygenic health conditions, caused by the combined effects of multiple genes or interactions between genes and the environment, often do not follow the traditional inheritance patterns. Examples include heart disease, type 2 diabetes, schizophrenia, and certain types of cancer. Additionally, disorders resulting from changes in chromosome number or structure also do not follow the traditional inheritance patterns.

One mutated copy of a gene in each cell is enough to cause an autosomal dominant condition in an individual. This can happen to persons who have no family history of the condition and can be caused by a novel gene mutation. Although the parents of a person with an autosomal recessive disorder usually possess one copy of the mutated gene but do not exhibit the condition's symptoms, autosomal recessive inheritance happens when variations arise in both copies of the gene in each cell.

While females have two X chromosomes, men have only one. The X-linked dominant diseases are caused by variations in genes on the X chromosome. Fathers are unable to pass on X-linked features to their sons, while females may show milder signs of the illness than men. Additionally, X-linked recessive illnesses are caused by variations in genes on the X chromosome, and they afflict males more often than females.

When the disorder's mutated gene is found on the Y chromosome, one of the two sex chromosomes in each male cell, it is known as Y-linked inheritance. Two distinct gene variants (alleles) that produce slightly different proteins are expressed in codominant inheritance.

Mitochondrial inheritance, also known as maternal inheritance, applies to genes in mitochondrial DNA. Only females can pass on mitochondrial variants to their children, and conditions resulting from these variants can appear in every generation of a family and affect both males and females. [4][5]

Trust the Process

Genetics is a complex process that involves the interaction of multiple genes, including gametes, chromosomes, and genes. Gametes, such as sperm and eggs, are sex cells in humans. While DNA determines the characteristics of a living organism. Chromosomes, long threads of DNA, contain many genes, which code for specific amino acids to make a specific protein. Genes can be copied and passed on to the next generation.

Some characteristics are controlled by a single gene, such as fur in animals and red-green color blindness in humans. Each gene may have different forms, known as alleles. A genotype is the collection of alleles that determine characteristics and can be expressed as a phenotype. Alleles can be dominant or recessive. Dominant alleles are always expressed, while recessive alleles are only expressed if the individual has two copies and does not have the dominant allele. Homozygous and heterozygous alleles are identical for the same characteristic, while heterozygous alleles are different for the same characteristic. Most characteristics are a result of multiple genes interacting, rather than a single gene.

Genes are located on chromosomes, which are in pairs and contain their alleles. When a cell divides in half, each chromosome ends up in a different cell, creating egg cells or sperm. These genes split into two halves, called alleles. Meiosis is a series of cell divisions that creates haploid cells with half of the total number of chromosomes. Once the egg and sperm meet, the pairs are restored but the genetic combination of the pair is altered, leading to the inheritance of a defective gene causing a genetic disorder by offspring.

Genes need to be inherited independently of each other, but there are far more genes than chromosome pairs. All genes on a chromosome are physically inherited together as a single linked group during meiosis. According to the chromosomal theory, 25% would resemble one parent, 25% would have one trait from one parent and one from the other, and 25% would have the "other" traits from each parent. Genes on different chromosomes assort independently during sexual reproduction, recombining to form new combinations of genes.

Crossover, a process where chromosomes exchange stretches of DNA, shuffles gene alleles between chromosomes. The probability of crossover occurring between two given points on the chromosome is related to the distance between the points. For genes closer together, the lower probability of crossover means that the alleles for the two genes tend to be inherited together. [1][3]