Year 10 Science: Genetics, Evolution, and Geological Time

Vocabulary practice cards covering Genetics, DNA structure, Cell Division, Inheritance patterns, Fossils, Dating techniques, and Evolution concepts from Year 10 Science.

DNA

Deoxyribonucleic acid; a molecule that determines a person’s characteristics and has a similar structure in all organisms.

Nucleotides

The building blocks of DNA, containing a phosphate group, a deoxyribose sugar, and one of four nitrogen-rich bases.

Double helix

The shape of DNA, described by James Watson and Francis Crick, which resembles a twisted rope ladder.

Nitrogen-rich bases

The four chemicals in DNA: adenine (A), thymine (T), guanine (G), and cytosine (C).

Nitrogen-rich base pairs

Bases occurring as adenine with thymine ($A-T$) and guanine with cytosine ($G-C$) due to their chemical composition.

Chromosomes

Long, thin, threadlike structures found in the nucleus of cells.

Sex chromosomes

The last pair of chromosomes ($XX$ for girl, $XY$ for boy) that determine the gender of an individual.

Gametes

Sex cells (sperm and eggs) that contain only $23$ chromosomes in humans.

Genes

Sections of DNA that code for specific characteristics by helping code for proteins.

Rosalind Franklin

The scientist who used X-ray crystallography to take an image of DNA, which was later shown to Watson and Crick by Maurice Wilkins.

Replication

The process of making new cells essential for growth, repair, or reproduction of damaged tissue.

Mitosis

Cell division that produces $2$ daughter cells identical to the parent cell, involved in growth and repair.

Meiosis

Cell division that produces $4$ daughter cells (gametes) with half the number of chromosomes ($n$) of the parent cell ($2n$).

Diploid number

The number of chromosomes in body cells, described as $2n$ ($46$ in humans).

Haploid number

The number of chromosomes in gametes, described as $n$ ($23$ in humans).

Homologous chromosomes

Chromosomes that are the same length, have the centromere at the same position, and possess genes for particular characteristics at the same location.

Autosomes

All the chromosomes in a cell other than the sex chromosomes.

Centromere

The point on a chromosome where two chromatids are held together.

Chromatid

One of the two strands of a chromosome following replication, containing one double helix.

DNA helicase

An enzyme that separates the double helix by breaking the hydrogen bonds connecting the N-bases during replication.

Somatic cells

All cells in the body except for the sex cells.

Asexual reproduction

The production of offspring through mitosis without the union of gametes, seen in organisms like Hydra and grass.

Alleles

Different forms of the same gene located at the same spot on homologous chromosomes.

Pure breeding

When all individuals have the same genetic information for a characteristic across generations.

Gregor Mendel

Scientist who studied pea plants ($Pisum\,sativum$) and found that traits are controlled by discrete units (genes) that segregate independently.

Homozygous

Having two identical alleles on homologous chromosomes (e.g., $rr$ or $RR$).

Heterozygous

Having two different alleles on homologous chromosomes (e.g., $Rr$).

Phenotype

The observable characteristics of an individual, which is the way the genotype is expressed.

Genotype

The genetic information carried by an individual.

Sex-linked genes

Genes present on the sex chromosomes, most often found on the longer X chromosome.

Hemophilia

A recessive sex-linked disease that prevents blood clotting, making even small wounds life-threatening.

Pedigree

An ancestral line depicting the lineage of an individual.

Mutations

Mistakes in the manufacture of proteins caused by changes in the DNA base sequence, which can be caused by UV, radiation, or chemicals.

Silent mutation

A change in the genetic code that does not affect the individual or the protein produced.

Nonsense mutation

A mutation that causes the cell to stop reading information prematurely, resulting in an incomplete, non-functional protein (e.g., Cystic fibrosis).

Frameshift mutation

A mutation caused by the insertion or deletion of a single base, jumbling all following genetic information (e.g., Tay-Sach’s disease).

Gene splicing

The process used to add or remove specific genes from DNA.

Plasmid

A ring of DNA found in bacteria used in recombinant DNA technology.

Human Genome Project

An international project ($1990-2003$) that aimed to identify all human genes and sequence the $3$ billion base pairs of human chromosomes.

Amniocentesis

A procedure where amniotic fluid is extracted to isolate foetal cells for genetic testing.

Gene therapy

An experimental technique where a defective gene is replaced with a normal one to cure a genetic disease.

Pluriopotent stem cells

Pluripotent cells found in early embryos that are capable of becoming any of the $220$ different cell types in the body.

iPSCs

Induced pluripotent skin cells; mature skin cells returned to a pluripotent state, discovered by Shinya Yamanaka in $2006$.

Fossils

Preserved remains or impressions of living organisms found in sedimentary rock.

Paleontology

The study of past life on Earth, especially through the analysis of fossils.

Replacement fossils

Fossils formed when part of an organism is chemically changed into another mineral, such as silica.

Trace fossils

Indirect fossils that are imprints rather than preserved remains, such as footprints, tracks, or fossilized dung.

Mould

An indirect fossil that is an imprint left in a rock showing the outside of an organism, creating a negative image.

Cast

A $3D$ model of an organism's body formed when a mould is filled with sediment and turned into rock.

Relative dating

A technique comparing the age of one fossil or rock with another based on sedimentary strata layers.

Fluorine analysis

A dating method that compares the fluorine absorbed by bones from water; higher fluorine content indicates an older specimen.

Index fossils

Fossils of organisms that lived for a short, well-defined time span over a wide area, used to date rock layers (e.g., trilobites and ammonites).

Absolute dating

Dating techniques, such as radioactive dating or tree ring counting, that provide the actual age of rocks and fossils.

Carbon-14 half-life

The time required for half the Carbon-14 in an organism to decay, which is $5730$ years.

Stromatolites

Circular rocky structures formed by cyanobacteria, which are thought to be the earliest evidence of life on Earth.

Tetrapods

The group of all land animals with four legs.

Archaeopteryx

A bird-like dinosaur with feathers that represents a transitional form between reptiles and birds.

Evolution

The change in characteristics of a species over many generations, potentially resulting in the formation of new species.

Homologous structures

Characteristics in related species that share the same basic structure and genetic control, such as pentadactyl limbs in humans and bats.

Analogous structures

Features in different species that perform similar functions but lack a common evolutionary origin, such as the fins of sharks and dolphins.

Natural selection

The process where an environmental selective agent acts on a population, resulting in some organisms having more offspring than others.

Speciation

The process split into three steps (variation, isolation, and selection) where one species splits into two or more distinct species.

Cytochrome c

A protein found in all organisms used by scientists to compare amino acid sequences to determine evolutionary similarity.

IVF

In Vitro Fertilization; a procedure where eggs are stimulated by follicle stimulating hormone (FSH) and fertilized with sperm in a petri dish at $38^{\circ}C$.