Genetics basics
58 flashcards covering Genetics basics for the ACT Science section.
Genetics is the study of how traits, like eye color or height, are passed from parents to offspring through units called genes, which are segments of DNA. At its core, it explains inheritance patterns and the variations that make each organism unique. This field helps us understand everything from basic family resemblances to more complex evolutionary changes, making it a foundational topic in biology.
On the ACT Science section, genetics questions often appear in data analysis or research summaries, where you'll interpret graphs, Punnett squares, or pedigrees to predict outcomes of genetic crosses. Common traps include confusing dominant and recessive traits or overlooking environmental influences on gene expression, so pay close attention to details in passages. Focus on key concepts like alleles, genotypes, and phenotypes to answer questions accurately and avoid misinterpretations.
A helpful tip: Practice sketching Punnett squares to quickly visualize inheritance patterns.
Terms (58)
- 01
Gene
A segment of DNA that contains the instructions for building a specific protein or RNA molecule, determining a particular trait in an organism.
- 02
Allele
One of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome.
- 03
Dominant allele
An allele that expresses its trait even when only one copy is present, masking the effect of a recessive allele in a heterozygous individual.
- 04
Recessive allele
An allele that only expresses its trait when two copies are present, meaning the individual must be homozygous for it.
- 05
Genotype
The genetic makeup of an organism, represented by the specific alleles it carries for a particular gene or set of genes.
- 06
Phenotype
The observable characteristics of an organism, resulting from the interaction of its genotype with the environment.
- 07
Homozygous
Describes an individual that has two identical alleles for a specific gene, either both dominant or both recessive.
- 08
Heterozygous
Describes an individual that has two different alleles for a specific gene, one dominant and one recessive.
- 09
Punnett square
A grid used to predict the probabilities of different genotypes and phenotypes in offspring from a genetic cross between two parents.
- 10
Monohybrid cross
A breeding experiment that tracks the inheritance of a single trait, such as flower color, to observe patterns like dominant and recessive expression.
- 11
Dihybrid cross
A breeding experiment that tracks the inheritance of two traits simultaneously, showing how different genes assort independently.
- 12
Law of Segregation
Mendel's principle stating that during gamete formation, the two alleles for each gene separate, so each gamete carries only one allele for that gene.
- 13
Law of Independent Assortment
Mendel's principle indicating that alleles of different genes assort independently of one another during gamete formation.
- 14
DNA
Deoxyribonucleic acid, the molecule that carries the genetic instructions for the development, functioning, and reproduction of all known living organisms.
- 15
Chromosome
A thread-like structure of DNA and proteins that carries genetic information in the form of genes, found in the nucleus of cells.
- 16
Nucleotide
The basic building block of nucleic acids like DNA and RNA, consisting of a sugar, a phosphate group, and a nitrogenous base.
- 17
Double helix
The twisted-ladder structure of DNA, where two strands are held together by hydrogen bonds between complementary base pairs.
- 18
Base pairing
The specific hydrogen bonding between nitrogenous bases in DNA, where adenine pairs with thymine and guanine pairs with cytosine.
- 19
Transcription
The process by which the information in a strand of DNA is copied into a new molecule of messenger RNA.
- 20
Translation
The process by which the genetic code in messenger RNA is read to make a specific protein in the ribosome.
- 21
Mutation
A change in the DNA sequence of an organism's genome, which can lead to variations in traits and potentially affect evolution.
- 22
Incomplete dominance
A pattern of inheritance where neither allele is completely dominant, resulting in a blended phenotype in heterozygous individuals.
- 23
Codominance
A pattern of inheritance where both alleles in a heterozygous individual are fully expressed, leading to a phenotype that shows both traits equally.
- 24
Polygenic traits
Characteristics determined by more than one gene, such as height or skin color, resulting in a range of phenotypes rather than discrete categories.
- 25
Sex-linked trait
A genetic characteristic carried on the sex chromosomes, often the X chromosome, leading to different inheritance patterns in males and females.
- 26
Autosomal dominant
A pattern of inheritance for a trait on a non-sex chromosome where only one copy of the allele is needed for the trait to be expressed.
- 27
Autosomal recessive
A pattern of inheritance for a trait on a non-sex chromosome where two copies of the allele are required for the trait to be expressed.
- 28
Meiosis
A type of cell division that produces gametes with half the number of chromosomes, ensuring genetic diversity through processes like crossing over.
- 29
Mitosis
A process of cell division that results in two identical daughter cells, each with the same number of chromosomes as the parent cell.
- 30
Genetic variation
The diversity in DNA sequences among individuals of a species, arising from mutations, recombination, and other mechanisms.
- 31
Pedigree chart
A diagram that shows the inheritance of a particular trait over generations in a family, used to trace genetic patterns.
- 32
Karyotype
A visual representation of an individual's chromosomes, arranged by size and type, used to identify abnormalities like Down syndrome.
- 33
Genetic recombination
The exchange of genetic material between homologous chromosomes during meiosis, increasing genetic diversity.
- 34
RNA
Ribonucleic acid, a molecule similar to DNA that plays key roles in coding, decoding, regulation, and expression of genes.
- 35
Heredity
The passing of traits from parents to offspring through genetic information in DNA.
- 36
Genetics
The study of genes, heredity, and genetic variation in organisms.
- 37
Phenotypic ratio
The ratio of different phenotypes observed in offspring from a genetic cross, such as 3:1 in a monohybrid cross with complete dominance.
- 38
Genotypic ratio
The ratio of different genotypes in offspring from a genetic cross, like 1:2:1 for a monohybrid cross.
- 39
Carrier
An individual who has one copy of a recessive allele for a genetic disorder but does not exhibit the disorder, potentially passing it to offspring.
- 40
Test cross
A breeding experiment where an individual of unknown genotype is crossed with a homozygous recessive individual to determine the unknown genotype.
- 41
Linkage
The tendency for genes located close together on the same chromosome to be inherited together, rather than assorting independently.
- 42
Crossing over
The exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, which can create new allele combinations.
- 43
Pleiotropy
When a single gene influences multiple, seemingly unrelated phenotypic traits.
- 44
Epistasis
An interaction between two or more genes where one gene modifies the expression of another gene.
- 45
Strategy for Punnett squares
To solve genetics problems, first identify parent genotypes, set up the grid with possible gametes, and calculate offspring ratios based on combinations.
- 46
Common trap in inheritance
Assuming traits always follow simple dominant-recessive patterns; in reality, factors like incomplete dominance can produce unexpected phenotypes.
- 47
Worked example: Monohybrid cross
For parents Tt and tt, the Punnett square shows a 1:1 ratio of offspring genotypes Tt and tt, resulting in a 1:1 phenotypic ratio if T is dominant.
- 48
Worked example: Dihybrid cross
For parents AaBb and aabb, the Punnett square predicts a 1:1:1:1 genotypic ratio if genes assort independently, leading to varied phenotypes.
- 49
DNA replication
The process by which a cell makes an identical copy of its DNA before cell division, ensuring each daughter cell gets a complete set.
- 50
Codon
A sequence of three nucleotides in DNA or RNA that codes for a specific amino acid or signals the start or stop of protein synthesis.
- 51
Genetic code
The set of rules by which information encoded in mRNA sequences is translated into proteins, with most amino acids coded by multiple codons.
- 52
Point mutation
A type of mutation that changes a single nucleotide base in DNA, which can alter the amino acid sequence in a protein.
- 53
Frameshift mutation
A mutation caused by insertion or deletion of nucleotides not in multiples of three, shifting the reading frame and often disrupting the protein.
- 54
Natural selection in genetics
The process where genetic variations that enhance survival and reproduction become more common in a population over generations.
- 55
Gene pool
The complete set of genetic information in a population, including all alleles for all genes.
- 56
Population genetics
The study of how gene frequencies change in populations over time, influenced by factors like mutation and selection.
- 57
Hybrid
An offspring resulting from the cross between two individuals of different varieties or species, often showing heterozygous traits.
- 58
Backcross
A cross between an offspring and one of its parents or an individual genetically identical to a parent, used to analyze inheritance.