3b - Chromosomes, DNA and Genes

Alleles

等位基因 (děngwèi jīyīn) Different forms or versions of the same gene, found at the same locus (position) on homologous chromosomes. They code for different variations of a trait.

Anticodon

反密码子 (fǎnmìmǎzǐ) A sequence of three bases on a tRNA molecule that is complementary to a specific mRNA codon, ensuring the correct amino acid is added during protein synthesis.

Base

（含氮）碱基 ((hándàn) jiǎnjī) One of four nitrogen-containing molecules in DNA (Adenine, Thymine, Cytosine, Guanine - A, T, C, G) or RNA (Adenine, Uracil, Cytosine, Guanine - A, U, C, G). They form complementary pairs.

Base pairing rule

碱基互补配对原则 (jiǎnjī hùbǔ pèiduì yuánzé) The rule stating that in DNA, Adenine (A) always pairs with Thymine (T), and Cytosine (C) always pairs with Guanine (G). In RNA, Adenine (A) pairs with Uracil (U).

Chromosome

染色体 (rǎnsètǐ) A thread-like structure found in the nucleus, made of DNA tightly coiled around histone proteins. Carries genetic information in the form of genes.

Codons

密码子 (mìmǎzǐ) A sequence of three nucleotide bases on an mRNA molecule that codes for a specific amino acid or a stop signal during protein synthesis.

Deoxyribonucleic acid (DNA)

脱氧核糖核酸 (tuōyǎng hétáng hésuān) The molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms. It has a double helix structure.

Diploid (2n)

二倍体 (èrbèitǐ) Having two complete sets of chromosomes, one from each parent (e.g., in most somatic cells). Chromosomes exist in homologous pairs.

Dominant

显性（等位基因）(xiǎnxìng (děngwèi jīyīn)) An allele that is always expressed in the phenotype, even if only one copy is present (i.e., it masks the effect of a recessive allele in a heterozygote).

Fertilisation

受精 (shòujīng) The fusion of the nucleus of a male gamete (haploid) with the nucleus of a female gamete (haploid) to form a diploid zygote.

Gene

基因 (jīyīn) A segment of DNA on a chromosome that codes for a specific protein or functional RNA molecule, thereby controlling a particular characteristic or trait. The basic unit of heredity.

Genome

基因组 (jīyīnzǔ) The complete set of genetic material (DNA) present in an organism, including all of its genes.

Haploid (n)

单倍体 (dānbèitǐ) Having a single set of unpaired chromosomes (e.g., in gametes).

Histone

组蛋白 (zǔdànbái) Proteins around which DNA is coiled to form chromatin, helping to package and organize DNA within chromosomes.

Homologous pairs

同源染色体 (tóngyuán rǎnsètǐ) A pair of chromosomes (one inherited from each parent) that are the same size, shape, and carry genes for the same traits at the same loci, although the alleles for those traits may differ.

Meiosis

减数分裂 (jiǎnshù fēnliè) A type of cell division that produces four haploid daughter cells (gametes) from one diploid parent cell, involving two rounds of division. Essential for sexual reproduction.

Messenger RNA (mRNA)

信使RNA (xìnshǐ RNA) A type of RNA molecule that carries a copy of the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm, where it serves as a template for protein synthesis.

Protein Synthesis

蛋白质合成 (dànbáizhì héchéng) The process by which cells build proteins. It involves two main stages: transcription (DNA to mRNA) and translation (mRNA to protein at the ribosome).

Recessive

隐性（等位基因）(yǐnxìng (děngwèi jīyīn)) An allele that is only expressed in the phenotype if two copies are present (i.e., its effect is masked by a dominant allele in a heterozygote).

DNA Replication

（DNA）复制 ((DNA) fùzhì) The process by which a DNA molecule makes an identical copy of itself, occurring before cell division (mitosis or meiosis).

Ribonucleic acid (RNA)

核糖核酸 (hétáng hésuān) A nucleic acid similar to DNA but usually single-stranded, containing ribose sugar and uracil (U) instead of thymine (T). Involved in protein synthesis (mRNA, tRNA, rRNA).

Ribosomes

核糖体 (hétángtǐ) Small cellular organelles, made of ribosomal RNA (rRNA) and protein, that are the sites of protein synthesis (translation) in the cytoplasm.

Sex chromosomes

性染色体 (xìng rǎnsètǐ) Chromosomes that determine the sex of an individual (e.g., X and Y chromosomes in humans).

Template strand

（DNA）模板链 ((DNA) múbǎn liàn) The strand of DNA that is used as a template during transcription to synthesize a complementary mRNA molecule.

Transcription

转录 (zhuǎnlù) The process of creating a complementary mRNA copy of a gene from a DNA template in the nucleus.

Transfer RNA (tRNA)

转运RNA (zhuǎnyùn RNA) A type of RNA molecule that transports specific amino acids to the ribosome during protein synthesis, matching its anticodon to the mRNA codon.

Translation

翻译 (fānyì) The process by which the sequence of codons on an mRNA molecule is decoded at the ribosome to synthesize a specific protein with a corresponding sequence of amino acids.

Zygote

受精卵 (shòujīngluǎn) A diploid cell resulting from the fusion of two haploid gametes (fertilization); the first cell of a new individual.