Science Flashcards
Differentiate between somatic cells (diploid) and gametes cells (haploid) in the human body.
Somatic cells, also called body cells, make up most of your body tissues and organs.
Diploid means that a cell has two copies of each chromosome: one copy from the mother, and one copy from the father
Gametes are sex cells—ova, or eggs, in the female, and spermatozoa, or sperm cells, in then.
Haploid means that a cell has only one copy of each chromosome
Define and explain homologous chromosomes.
Homologous chromosomes are two chromosomes—one inherited from the mother, one from the father—that have the same length and general appearance. More importantly, these chromosomes have copies of the same genes, although the two copies may differ.
Explain the process of meiosis.
Meiosis is a form of nuclear division that divides a diploid cell into haploid cells.
This process is essential for sexual reproduction. Meiosis occurs in germ cells to produce gametes.
This process is sometimes called a “reduction division” because it reduces a cell’s chromosome number by half
Differentiate between the two types of gametes (egg vs. sperm.)
The sperm cell, the male gamete, is much smaller than the egg, the female gamete.
The sperm cell’s main contribution to an embryo is DNA; also contributes the organelles, molecular building blocks, and other materials an embryo needs to begin life.
Define and explain Mendel’s law of segregation.
- Organisms inherit two copies of each gene, one from each parent.
- Organisms donate only one copy of each gene in their gametes. Thus, the two copies of each gene segregate, or separate, during gamete formation.
Describe Mendel’s experimental process with pea plants.
Mendel chose pea plants for his experiments because they reproduce quickly, and he could easily control how they mate. The sex organs of a plant are in its flowers, and pea flowers contain both male and female reproductive organs. In nature, the pea flower mates with itself. If a line of plants has self-pollinated for long enough, that line becomes genetically uniform, or purebred. As a result, the offspring of purebred parents inherit all of the parent organisms’ characteristics. Mendel was able to mate plants with specific traits by interrupting the self-pollination process.
Because he started with purebred plants, Mendel knew that any variations in offspring resulted from his experiments. Mendel chose seven traits to follow: pea shape, pea color, pod shape, pod color, plant height, flower color, and flower position. All of these traits are simple “either-or” characteristics; they do not show intermediate features. The plant is tall or short. Its peas are wrinkled or round. What Mendel did not know was that most of the traits he had selected were controlled by genes on separate chromosomes. The selection of these particular traits played a crucial role in enabling Mendel to identify the patterns he observed.
Define and give examples of phenotype.
The physical characteristics, or traits, of an individual organism make up its phenotype.
Define and give examples of genotype.
A genotype typically refers to the genetic makeup of a specific set of genes.
Define, explain and give examples of dominant and recessive alleles.
A dominant allele is the allele that is expressed when two different alleles or two dominant alleles are present.
A recessive allele is the allele that is expressed only when two copies are present.
Define, explain and give examples of dominant/recessive traits.
A plant with smooth pods could have a homozygous dominant (SS) or heterozygous (Ss) genotype. In contrast, a plant with constricted, or compressed, pods could have only a homozygous recessive (ss) genotype.
Define, explain and give examples of homozygous and heterozygous alleles.
The term homozygous describes two of the same alleles at a specific locus.
The term heterozygous describes two different alleles at a specific locus.
Define and explain Mendel’s law of independent assortment.
The law of independent assortment states that allele pairs separate independently of each other during gamete formation, or meiosis. That is, different traits appear to be inherited separately.
Describe a Punnett Square and be able to solve problems involving Punnett Squares.
A Punnett square is a grid system for predicting all possible genotypes resulting from a cross.
Define and explain crossing over during meiosis.
Crossing over is the exchange of chromosome segments between homologous chromosomes during prophase I of meiosis I.
1- At this stage, each chromosome has been duplicated, the sister chromatids are still connected to each other, and homologous chromosomes have paired with each other.
2-When homologous chromosomes are in this position, some of the chromatids are very close to each other.
3- Part of one chromatid from each chromosome breaks off and reattaches to the other chromosome.
Define and explain gene linkage.
The gene linkage is when genes located close together tend to be inherited together.
Define and explain X chromosome inactivation.
When one of the two X chromosome in each cell of a female mammal turns off
Define and explain a carrier for a genetic disorder
A carrier is someone who does not have a disorder but carries the recessive allele, and therefore, can pass the allele on to offspring
Define polygenic traits and give examples.
Traits produced by two or more genes are called polygenic traits.
Examples: Human skin color, for example, is the result of four genes that interact to produce a continuous range of colors. Similarly, human eye color, which is often thought of as a single gene trait, is polygenic.
Define, explain and give examples of incomplete dominance.
Sometimes, alleles show incomplete dominance, in which a heterozygous phenotype is somewhere between the two homozygous phenotypes. Neither allele is completely dominant nor completely recessive.
